The Effects of Heat and Cold on Cognitive Function and Endurance Capacity

The maintenance of mental and physical function in hot and cold environments is more challenging compared to thermoneutral environments due to increases systemic physiological and psychological strain. The mechanism for impairments in both cognitive and physical function may be due to early perturbations in whole-body heat balance where the change in skin temperature (even before measurable changes in core temperature) impair performance, followed by greater impairments with changes in core temperature. However, the separate and combined effects of changes in skin and core temperature over a range of cognitive functions and exercise require further elucidation. Therefore, this dissertation tested cognitive function (psychomotor processing, working memory, and executive function) and endurance capacity (at 70% of peak power output) over a range of skin and core temperatures and thermal conditions. Chapter 4 investigates the effects of whole-body skin and core warming (hyperthermia) on cognitive function. In addition, the pharmacological drug, methylphenidate (20 mg, dopamine re-uptake inhibitor) was used as it may improve physiological and psychological strain during heat stress. Chapter 5 built upon Chapter 4 by testing the effects of whole-body skin and core cooling (mild hypothermia) on cognitive function. Chapter 6 extended the findings of Chapter 5 by testing the effects of whole-body skin and core cooling on endurance capacity, to potentially see a cognitive-physical performance interaction. Collectively, we found that neither changes in skin temperature (Range: ∆-6 to +4.5°C), without changes in core temperature, nor manipulation of core temperature (Range: ∆-0.8 to +1.5°C) significantly impaired cognitive function in hot or cold environments (Chapters 4 & 5). Furthermore, methylphenidate did not enhance cognitive function. Whereas, endurance capacity was significantly influenced by cold stress, where cooling the skin/outer shell impaired performance by 32%, while core cooling of ∆-0.5C and ∆-1.0C from baseline temperature further impaired performance by 61% and 71% respectively. There were no differences between the two core cooling conditions. Collectively, this research program demonstrates the capacity to maintain cognitive function, but not physical capacity under thermal strain. From a practical standpoint, interventions should focus to minimize cold strain to prevent declines in physical capacity under cold conditions

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo

International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M⊙, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M⊙ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M⊙ and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]† Deceased, August 2020