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Background: Aquatic viruses act as key players in shaping microbial communities. In polar environments, they face significant challenges such as limited host availability and harsh conditions. However, due to the restricted accessibility of these ecosystems, our understanding of viral diversity, abundance, adaptations, and host interactions remains limited. Results: To fill this knowledge gap, we studied viruses from atmosphere-close aquatic ecosystems in the Central Arctic and Northern Greenland. Aquatic samples for virus-host analysis were collected from ~60 cm depth and the submillimeter surface microlayer (SML) during the Synoptic Arctic Survey 2021 on icebreaker Oden in the Arctic summer. Water was sampled from a melt pond and open water before undergoing size-fractioned filtration, followed by genome-resolved metagenomic and cultivation investigations. The prokaryotic diversity in the melt pond was considerably lower compared to that of open water. The melt pond was dominated by a Flavobacterium sp. and Aquiluna sp., the latter having a relatively small genome size of 1.2 Mb and the metabolic potential to generate ATP using the phosphate acetyltransferase-acetate kinase pathway. Viral diversity on the host fraction (0.2–5 µm) of the melt pond was strikingly limited compared to that of open water. From the 1154 viral operational taxonomic units (vOTUs), of which two-thirds were predicted bacteriophages, 17.2% encoded for auxiliary metabolic genes (AMGs) with metabolic functions. Some AMGs like glycerol-3-phosphate cytidylyltransferase and ice-binding like proteins might serve to provide cryoprotection for the host. Prophages were often associated with SML genomes, and two active prophages of new viral genera from the Arctic SML strain Leeuwenhoekiella aequorea Arc30 were induced. We found evidence that vOTU abundance in the SML compared to that of ~60 cm depth was more positively correlated with the distribution of a vOTU across five different Arctic stations. Conclusions: The results indicate that viruses employ elaborate strategies to endure in extreme, host-limited environments. Moreover, our observations suggest that the immediate air-sea interface serves as a platform for viral distribution in the Central Arctic. Dvb_jZZ1H7pg55rxrDSVb2 Video Abstract [ABSTRACT FROM AUTHOR]

Summary: Although studies have shown that light affects sleep in polar populations, the sample size of most studies is small. This meta‐analysis provides the first systematic review of the effects of summer glare, spring and fall moderate daylight, and artificial lighting on general sleep problems (sleep duration, efficiency, and delay). This analysis included 18 studies involving 986 participants. We calculated the random effect size via an evidence‐based meta‐analysis that analysed the effect of bright/auxiliary light on sleep and the effect of three different types of light on sleep compared with conventional light. There was no significant correlation between specific light types and sleep duration. Intense summer light has a negative effect on sleep time and efficiency. Moderate, natural light in spring and autumn effectively delayed sleep but could not improve sleep efficiency. For artificial fill light, neither blue light nor enhanced white light has been found to have a significant effect. In summary, summer light has a detrimental effect on sleep in polar populations, and moderate natural light may be superior to conventional light. However, specific strategies to improve sleep and artificial lighting in polar populations must be explored further. [ABSTRACT FROM AUTHOR]

Abstract Background Aquatic viruses act as key players in shaping microbial communities. In polar environments, they face significant challenges such as limited host availability and harsh conditions. However, due to the restricted accessibility of these ecosystems, our understanding of viral diversity, abundance, adaptations, and host interactions remains limited. Results To fill this knowledge gap, we studied viruses from atmosphere-close aquatic ecosystems in the Central Arctic and Northern Greenland. Aquatic samples for virus-host analysis were collected from ~60 cm depth and the submillimeter surface microlayer (SML) during the Synoptic Arctic Survey 2021 on icebreaker Oden in the Arctic summer. Water was sampled from a melt pond and open water before undergoing size-fractioned filtration, followed by genome-resolved metagenomic and cultivation investigations. The prokaryotic diversity in the melt pond was considerably lower compared to that of open water. The melt pond was dominated by a Flavobacterium sp. and Aquiluna sp., the latter having a relatively small genome size of 1.2 Mb and the metabolic potential to generate ATP using the phosphate acetyltransferase-acetate kinase pathway. Viral diversity on the host fraction (0.2–5 µm) of the melt pond was strikingly limited compared to that of open water. From the 1154 viral operational taxonomic units (vOTUs), of which two-thirds were predicted bacteriophages, 17.2% encoded for auxiliary metabolic genes (AMGs) with metabolic functions. Some AMGs like glycerol-3-phosphate cytidylyltransferase and ice-binding like proteins might serve to provide cryoprotection for the host. Prophages were often associated with SML genomes, and two active prophages of new viral genera from the Arctic SML strain Leeuwenhoekiella aequorea Arc30 were induced. We found evidence that vOTU abundance in the SML compared to that of ~60 cm depth was more positively correlated with the distribution of a vOTU across five different Arctic stations. Conclusions The results indicate that viruses employ elaborate strategies to endure in extreme, host-limited environments. Moreover, our observations suggest that the immediate air-sea interface serves as a platform for viral distribution in the Central Arctic. Video Abstract

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Abstract Antarctic moss beds are sensitive to climatic conditions, and both their survival and community composition are particularly influenced by the availability of liquid water over summer. As Antarctic regions increasingly face climate pressures (e.g., changing hydrology and heat waves), advancing capabilities to efficiently and non‐destructively monitor water content in moss communities becomes a key research priority. Because of the complexity induced by multiple micro‐climatic drivers and its fragility, tracking the evolution and responses of moss bed moisture requires monitoring methods that are non‐intrusive, efficient, and spatially significant, such as the use of unoccupied aerial systems (UAS). In this study, we combine a multi‐species drying laboratory experiment with short‐wave infrared (SWIR) spectroscopy analyses to first develop a Random Forest regression Model (RFM) capable of predicting Antarctic moss turf water content (~5% error). The RFM was then applied to UAS‐borne SWIR imaging data (900–1700 nm,

This study characterized cultivable fungi present in sediments obtained from Boeckella Lake, Hope Bay, in the north-east of the Antarctic Peninsula, and evaluated their production of enzymes and biosurfactants of potential industrial interest. A total of 116 fungal isolates were obtained, which were classified into 16 genera within the phyla Ascomycota, Basidiomycota and Mortierellomycota, in rank. The most abundant genera of filamentous fungi included Pseudogymnoascus, Pseudeurotium and Antarctomyces; for yeasts, Thelebolales and Naganishia taxa were dominant. Overall, the lake sediments exhibited high fungal diversity and moderate richness and dominance. The enzymes esterase, cellulase and protease were the most abundantly produced by these fungi. Ramgea cf. ozimecii, Holtermanniella wattica, Leucosporidium creatinivorum, Leucosporidium sp., Mrakia blollopis, Naganishia sp. and Phenoliferia sp. displayed enzymatic index > 2. Fourteen isolates of filamentous fungi demonstrated an Emulsification Index 24% (EI24%) ≥ 50%; among them, three isolates of A. psychrotrophicus showed an EI24% > 80%. Boeckella Lake itself is in the process of drying out due to the impact of regional climate change, and may be lost completely in approaching decades, therefore hosts a threatened community of cultivable fungi that produce important biomolecules with potential application in biotechnological processes. [ABSTRACT FROM AUTHOR]

We studied the culturable fungal community recovered from deep marine sediments in the maritime Antarctic, and assessed their capabilities to produce exoenzymes, emulsifiers and metabolites with phytotoxic activity. Sixty-eight Ascomycota fungal isolates were recovered and identified. The most abundant taxon recovered was the yeast Meyerozyma guilliermondii, followed by the filamentous fungi Penicillium chrysogenum, P. cf. palitans, Pseudeurotium cf. bakeri, Thelebolus balaustiformis, Antarctomyces psychrotrophicus and Cladosporium sp. Diversity indices displayed low values overall, with the highest values obtained at shallow depth, decreasing to the deepest location sampled. Only M. guilliermondii and P. cf. palitans were detected in the sediments at all depths sampled, and were the most abundant taxa at all sample sites. The most abundant enzymes detected were proteases, followed by invertases, cellulases, lipases, carrageenases, agarases, pectinases and esterases. Four isolates showed good biosurfactant activity, particularly the endemic species A. psychrotrophicus. Twenty-four isolates of P. cf. palitans displayed strong phytotoxic activities against the models Lactuca sativa and Allium schoenoprasum. The cultivable fungi recovered demonstrated good biosynthetic activity in the production of hydrolytic exoenzymes, biosurfactant molecules and metabolites with phytotoxic activity, reinforcing the importance of documenting the taxonomic, ecological and biotechnological properties of fungi present in deep oceanic sediments of the Southern Ocean. [ABSTRACT FROM AUTHOR]

Photostasis is the light-dependent maintenance of energy balance associated with cellular homeostasis in photoautotrophs. We review evidence that illustrates how photosynthetic adaptation in polar photoautrophs such as aquatic green algae, cyanobacteria, boreal conifers as well as terrestrial angiosperms exhibit an astonishing plasticity in structure and function of the photosynthetic apparatus. This plasticity contributes to the maintenance of photostasis, which is essential for the long-term survival in the seemingly inhospitable Antarctic and Arctic habitats. However, evidence indicates that polar photoautrophic species exhibit different functional solutions for the maintenance of photostasis. We suggest that this reflects, in part, the genetic diversity symbolized by inherent genetic redundancy characteristic of polar photoautotrophs which enhances their survival in a thermodynamically challenging environment. [ABSTRACT FROM AUTHOR]

The Arctic is impacted by some of the fastest temperature changes observed on Earth, but the impact on the terrestrial arthropod fauna is unclear. Acute physiological thermal limits of terrestrial ectotherms from high latitudes often exceed the local air temperatures, suggesting that they may be able to cope with increasing temperatures. However, knowledge on how Arctic terrestrial arthropods cope with elevated temperatures for longer periods is lacking.Here we investigate how acclimation temperature and exposure time affect the acute physiological heat tolerance of five terrestrial arthropod species (Neomolgus littoralis, Megaphorura arctica, Nysius groenlandicus, Psammotettix lividellus and Nabis flavomarginatus) immediately after collection in Arctic and sub‐Arctic habitats.We show that although acute heat tolerances are relatively high, even exposure to moderate (temperature span assessed ca. 3–29°C) acclimation temperatures for a 24 h period have strong negative effects on heat tolerance for four of the five species. Similarly, exposure time negatively affected heat tolerance, but depending on species and temperature.Together our results suggest that exposure to even moderately elevated temperatures for periods of 24 h or even shorter can lead to lower acute heat tolerance for cold adapted terrestrial arthropod species from sub‐Arctic and Arctic regions. Consequently, climate change leading to extended periods of mildly elevated temperatures may have strong negative effects on these species. We argue that this aspect is currently overlooked when assessing the ability of arthropods from Arctic and sub‐Artic regions to cope with climate changes as such predictions are typically based on acute heat tolerance estimates and with the assumption of beneficial acclimation responses. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The discrete Legendre transform is a powerful tool for analyzing the properties of convex lattice sets. In this paper, for t > 0 , we study a class of convex lattice sets and establish a relationship between vertices of the polar of convex lattice sets and vertices of the polar of its t − dilation. Subsequently, we show that there exists a class of convex lattice sets such that its polar is itself. In addition, we calculate upper and lower bounds for the discrete Mahler product of a class of convex lattice sets. [ABSTRACT FROM AUTHOR]

Aim: The rapidly changing Arctic is ideal for investigating uncertainties in climate projections. Despite the challenges of collecting data in this region, an unprecedented large‐scale survey of shorebirds has been conducted over the last 30 years. Our study aimed to (1) develop probabilistic estimates for the change in suitable habitat for 10 Arctic shorebird species in Canada by 2075 and (2) assess the contribution of modelling decisions to the uncertainty in these estimates. Location: Arctic Canada. Methods: To evaluate uncertainty, we considered six classes of modelling decisions, yielding 216 unique projections for each species. We tested three decisions that are less commonly explored − the pool of candidate variables, a method for selecting variables, and the maximum distance of tree line dispersal, as well as the modelling algorithm, carbon emissions scenario, and global circulation model. We used a bootstrapping approach, creating a probability distribution for the proportional change in suitable habitat for each species. Results: Our findings indicated a substantial risk for 8/10 species to lose over half of their suitable breeding habitat, but this projection is much less certain than has been described previously. While much uncertainty is unexplained, we were surprised that the largest source of uncertainty among our modelling decisions was from our choice of methods for variable selection, that the other modelling decisions were relatively small sources of uncertainty, overshadowing other modelling decisions. Main Conclusions: While most scenarios predict a northward shift and significant habitat loss for Arctic‐breeding shorebirds, the Arctic Archipelago of Canada will remain an important refuge because in many other Arctic regions, there is no land farther north for these species to shift into. A comprehensive understanding of uncertainty is important for deciding if future projections can or should be used when planning climate‐resilient protected area networks. [ABSTRACT FROM AUTHOR]

Polar systems are experiencing major changes that has significant implications for ocean circulation and global biogeochemistry. While these changes are accelerating, access to polar systems is decreasing as ships and logistical capabilities are declining. Autonomous underwater buoyancy gliders have proven to be robust technologies that are capable of filling sampling gaps. Gliders have also provided a more sustained presence in polar seas than ships are able. Along the West Antarctic Peninsula, one of the most rapidly warming regions on this planet, gliders have proven to be a useful tool being used by the international community to link land research stations without requiring major research vessel ship support. The gliders are capable of adaptive sampling of subsurface features not visible from satellites, sustained sampling to characterize seasonal dynamics, and they increasingly play a central role in themanagement of natural resources. Future challenges to expand their utility include: (A) developing robust navigation under ice, which would allow gliders to provide a sustained bridge between the research stations when ship support is declining, and (B) expanding online resources to provide the international community open access to quality data in near real time. These advances will accelerate the use of gliders to fill critical sampling gaps for these remote ocean environments. [ABSTRACT FROM AUTHOR]

Antarctic moss beds are sensitive to climatic conditions, and both their survival and community composition are particularly influenced by the availability of liquid water over summer. As Antarctic regions increasingly face climate pressures (e.g., changing hydrology and heat waves), advancing capabilities to efficiently and non‐destructively monitor water content in moss communities becomes a key research priority. Because of the complexity induced by multiple micro‐climatic drivers and its fragility, tracking the evolution and responses of moss bed moisture requires monitoring methods that are non‐intrusive, efficient, and spatially significant, such as the use of unoccupied aerial systems (UAS). In this study, we combine a multi‐species drying laboratory experiment with short‐wave infrared (SWIR) spectroscopy analyses to first develop a Random Forest regression Model (RFM) capable of predicting Antarctic moss turf water content (~5% error). The RFM was then applied to UAS‐borne SWIR imaging data (900–1700 nm, <16 nm spectral resolution) of the moss beds at high spatial resolution (2 cm) across three sites in the vicinity of Casey Station, Antarctica. The sites differed in terrain, snow cover, and moisture availability to evaluate method capabilities under different conditions. Optimum RFM parameters and input variables (spectral indices and reflectance spectra) were determined. Maps of moss moisture were validated via acquiring moss spectra and water content (using sponges inserted into the moss turf) collected in situ, for which an exponential correlation (R2 = 0.72) was reported. RFM further allowed investigation of the influential spectral variables to model water content in moss and associated spectral water absorption features. We demonstrated that UAS‐borne SWIR imaging is a promising new tool to map and quantify water content in Antarctic moss beds. Hyperspectral mapping facilitates the exploration of the spatial variability of moss health and enables the creation of a baseline against which changes in these moss communities can be measured. [ABSTRACT FROM AUTHOR]

Arctic terrestrial invertebrate biodiversity is generally poorly known, but the archipelago of Svalbard has one of the most up-to-date inventories of its terrestrial and freshwater faunas of any Arctic region, offering a baseline for long term monitoring of invertebrate communities in space and time. Since the most recent review of the Svalbard invertebrate fauna was produced in 2014, knowledge of this fauna has developed and this inventory is here critically revised and updated. Our aims are (1) to critically review the inventory based on current taxonomic knowledge, (2) publish the complete species inventory, including cross-referencing to the relevant publications, in an open access data archive (GBIF), and (3) highlight the particular advantages that working in Svalbard may bring for scientists working on terrestrial, freshwater, and cryospheric environments. The inventory contains a total 1091 valid species names or interim names. A gap analysis in the Barcode of Life Data Systems reveals that 50% of the species currently documented from Svalbard lack COI (Cytochrome c oxidase subunit 1) barcode reference sequences in this database. Gaps in our knowledge of the Svalbard fauna and how these may be resolved are discussed.

Foxes (Vulpes spp.) are small, solitary canids with relatively low social complexity compared to more gregarious canids, such as wolves and dogs. They are, therefore, expected to have a relatively simple vocal repertoire, with limited low-intensity sounds for close communication and many high-intensity sounds for long-distance communication. Arctic foxes (Vulpes lagopus), like many other foxes, are largely solitary outside of the breeding season. However, they have the largest litter size in the order Carnivora and may experience enhanced social complexity during the breeding season. In this study, we document the vocal repertoire of the Arctic fox during the breeding season, and how it changes before and after the emergence of pups. We also describe the relationship between vocalizations and other denning behaviours. Camera-traps captured six distinct sounds produced by breeding pairs of Arctic foxes and their young at dens: territorial barks, warning barks, alarm calls, cooing, whines and growling. Our study shows that although high-intensity sounds, such as territorial barks, are an important form of long-distance communication among Arctic foxes, low-intensity sounds and sound mixing are used on their dens following pup emergence. Thus, Arctic fox vocalization may be more complex than previously documented.

The fluid ferroelectrics, called ferroelectric nematics (NF), have recently become available by incorporating strong polarity into rod-shaped liquid crystal molecules. Its unprecedented electro-optic properties have created significant excitement in soft matter research. The further progression from the NF phase to the antiferroelectric smectic Z (SmZA) phase, and ultimately to the ferroelectric Smectic A (SmAF) phase, represents a remarkable journey in emerging polar liquid crystal states. Nevertheless, the limitation of NF liquid crystal materials remains one of the prominent obstacles to physical property optimization and optoelectronic device development. In this work, we synthesized a series of fluorinated liquid crystal molecules with large dipole moments and systematically investigated their phase behavior. We designed them with a similar fluorinated aromatic skeleton and varied the structures of the terminal group and bridging bond. We found that the dipole moment density and shape anisotropy significantly affect the phase behavior. Notably, diverse polar liquid crystal phases, including NF, SmZA, and SmAF were observed. Through a multi-component mixing strategy, we successfully achieved a much-expanded temperature window and improved low-temperature stability not only in the NF phase but also in the SmZA and SmAF phases. [ABSTRACT FROM AUTHOR]

Let L be a truncated Archimedean vector lattice whose truncation is denoted by *. In a recent paper, we proved that there exists a locally compact Hausdorff space X such that L is a lattice isomorphic with a truncated vector lattice of functions in C∞(X) whose truncation is provided by meet with some characteristic function on X. This representation, no matter how interesting it is, has a major drawback, namely, C∞(X) need not be a vector lattice, unless X is extremally disconnected. The main purpose of this paper is to remedy this shortcoming by proving that, indeed, an extremally disconnected locally compact space X can be found such that L can be seen as an order dense vector sublattice of C∞(X) whose truncation is provided, again, by meet with some characteristic function on X. [ABSTRACT FROM AUTHOR]

Icebergs and ice islands (large, tabular icebergs) present a significant hazard to marine vessels and infrastructure at a time when demand for access to Arctic waters is increasing. There is a growing demand for in situ iceberg tracking data to monitor their drift trajectories and improve models used for operational forecasting of ice hazards, yet the high cost of commercial tracking devices often prevents monitoring at optimal spatial and temporal resolutions. Here, we provide a detailed description of the Cryologger Ice Tracking Beacon (ITB), a low-cost, robust, and user-friendly data logger and telemeter for tracking icebergs and ice islands based on the Arduino open-source electronics platform. Designed for deployments of at least 2 years with an hourly sampling interval that is remotely modifiable by the end user, the Cryologger ITB provides long-term measurements of position, temperature, pressure, pitch, roll, heading, and battery voltage. Data are transmitted via the Iridium satellite network at user-specified intervals. We present the results of field campaigns in 2018 and 2019, which saw the deployment of 16 ITBs along the coasts of Greenland and Ellesmere and Baffin islands. The overall success of these ITB deployments has demonstrated that inexpensive, open-source hardware and software can provide a reliable and cost-effective method of monitoring icebergs and ice islands in the polar regions. [ABSTRACT FROM AUTHOR]

Introduction: The Arctic sea ice extent in September (when it is at its lowest) has declined 13% Q10 per decade, and the Arctic Ocean is becoming a more Atlantic-influenced system. Rapid climate-forced changes are taking place in many high-latitude marine ecosystems. The Barents Sea is one such highlatitude shelf ecosystem, between approximately 70° and 80°N in the Norwegian Arctic. The purpose of the current study was to estimate zoobenthic blue carbon across multiple habitats within the Barents Sea (trough, basin, shelf, and shallows), potentially providing values to aid ecosystem-based management of these areas under future climate change scenarios. Method: We tested this by capture and analysis of 947 high-resolution (each 405.7 × 340.6 mm, 12 MB, 5 megapixels) seabed images at 17 sites with latitudinal cline, linked to a collection of corresponding oceanographic data. Biotas within these images were identified to one of the 14 functional groups and the density was calculated. Mean stored carbon per individual was assigned by ash mass (AM) and ash-free dry mass (AFDM) of individuals caught within Agassiz trawl deployments at the same sites. Results: Trough sites, except for one site (B16), have a low quantity of zoobenthic blue carbon compared with the shallow, shelf, and basin habitats. Discussion: The results of a previous study focused entirely on trough habitats and are therefore difficult to scale up as the basis for a meaningful estimate of across-habitat zoobenthic blue carbon in the Barents Sea. Compared with the trough and the basin, the shelf and shallow habitats of the Barents Sea are also subjected to more trawling events through demersal fisheries and showed higher zoobenthic blue carbon stock values. [ABSTRACT FROM AUTHOR]

Fleshy macroalgae dominate the hard bottom, shallow waters along the Western Antarctic Peninsula (WAP). Although there are numerous reports on their ecology, geographic distribution, and to a lesser extent, vertical (depth) distribution in the northern portions of the WAP, much less is known farther south along the central portion of the WAP. Here we provide the first report of the vertical distributions of brown and red fleshy macroalgae in this region based on scuba-derived collections at 14 study sites between southern Anvers Island (64.8°S, 64.4°W) in the north and central Marguerite Bay (68.7°S, 67.5°W) in the south. Although several overstory brown macroalgal species that can be common along the northern WAP including Desmarestia anceps and Cystosphaera jacquinotii are mostly absent from the central WAP, the vertical distributions of the brown macroalgae Desmarestia menziesii and Himantothallus grandifolius are similar to the northern WAP even though their percent cover is much lower. Likewise, the vertical distribution of the 14 most widespread red macroalgae, where they occur, mirrored those known from the northern part of the WAP even though macroalgal cover, biomass, and total species richness declined markedly to the south across this region due to increasing sea ice concentrations. [ABSTRACT FROM AUTHOR]

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Southern social imaginaries have typically conceived of the North as a frozen and inhospitable area, depriving it of much interest. However, during the first part of the 20th century, the anthropologist and explorer Vilhjalmur Stefansson unveiled many mysteries about the Arctic. Throughout his life and writings, he tried to modify many inaccurate and now old-fashioned imaginings and imaginaries about the Arctic. The concept of the Polar Mediterranean Imaginary was thus proposed by him, whereby the Arctic region could be seen as a place similar to the Mediterranean region, i.e., an important socio-cultural, economic and political hub. Past and present events (e.g., global conflicts, scientific and technologic developments) contribute also to determining how the Arctic is shaped and understood today. The contemporary twin trends of globalization and climate change are making the North more and more globally connected and interconnected, especially through the rise of transpolar routes, which represent an opportunity for the affirmation of the Arctic’s central role, precisely along the lines envisioned by Vilhjalmur Stefansson and his Polar Mediterranean Imaginary one hundred years ago.

This article is a Commentary on Joli et al. (2024), 241: 2193–2208. [ABSTRACT FROM AUTHOR]

The discrete Legendre transform is a powerful tool for analyzing the properties of convex lattice sets. In this paper, for t>0, we study a class of convex lattice sets and establish a relationship between vertices of the polar of convex lattice sets and vertices of the polar of its t−dilation. Subsequently, we show that there exists a class of convex lattice sets such that its polar is itself. In addition, we calculate upper and lower bounds for the discrete Mahler product of a class of convex lattice sets.

L’enjeu principal de cette réflexion consiste à proposer une lecture sociopoétique de la figure de l’enquêteur dans le polar d’Afrique francophone, en partant de l’hypothèse que celle-ci apparaît comme l’un des moyens privilégiés de contestation sociale, politique et culturelle. De l’enquêteur déçu, intermédiaire au forban hilare, l’on remarque que le polar d’Afrique francophone se caractérise par le dédoublement de l’enquête, la réécriture du passé et la convocation de divers types de savoirs qui constituent le renouvellement du discours littéraire africain. Cette perspective sociopoétique vise ainsi à montrer que l’intrigue policière relève d’abord d’une énonciation littéraire qui tente de dire et comprendre le fonctionnement social et culturel des sociétés africaines contemporaines

ABSTRACT The infection cycle of phage λ terminates in lysis mediated by three types of lysis proteins, each disrupting a layer in the bacterial envelope: the S105 holin, the R endolysin, and the Rz/Rz1 spanin complex targeting the inner membrane, cell wall or peptidoglycan, and the outer membrane, respectively. Video microscopy has shown that in most infections, lysis occurs as a sudden, explosive event at a cell pole, such that the initial product is a less refractile ghost that retains rod-shaped morphology. Here, we investigate the molecular basis of polar lysis using time-lapse fluorescence microscopy. The results indicate that the holin determines the morphology of lysis by suddenly forming two-dimensional rafts at the poles about 100 s prior to lysis. Given the physiological and biochemical similarities between the lambda holin and other class I holins, dynamic redistribution and sudden concentration may be common features of holins, probably reflecting the fitness advantage of all-or-nothing lysis regulation.IMPORTANCEIn this study, we use fluorescent video microscopy to track -green fluorescent protein (GFP)-labeled holin in the minutes prior to phage lysis. Our work contextualizes prior genetic and biochemical data, showing when hole formation starts and where holin oligomers form in relation to the site of lytic rupture. Furthermore, prior work showed that the morphology of lambda-infected cells is characterized by an explosive event starting at the cell pole; however, the basis for this was not clear. This study shows that holin most often oligomerizes at cell poles and that the site of the oligomerization is spatially correlated with the site of lytic blowout. Therefore, the holin is the key contributor to polar lysis morphology for phage lambda.

ABSTRAK Jaringan 5G telah menjadi penanda penting dalam evolusi teknologi nirkabel yang menawarkan kecepatan dan kinerja yang luar biasa untuk memenuhi kebutuhan konektivitas yang semakin meningkat. Dalam jaringan 5G, pengkodean kanal merupakan elemen penting dalam memastikan pengiriman data yang handal dan efisien. Penelitian ini mengkaji sistem 5G pada frekuensi 26 GHz dan bandwidth 200 MHz menggunakan Orthogonal Frequency Division Multiplexing (OFDM) dengan ukuran Fast Fourier Transform (FFT) sebesar 256 dan modulasi Binary Phase Shift Keying (BPSK). Penelitian ini mengevaluasi perbandingan penambahan channel coding yaitu QC-LDPC dan polar codes. Performansi QC-LDPC codes pada BER sebesar 10-4 dapat dicapai dengan SNR 𛾠= 17 ð‘‘ðµ untuk kode QC-LDPC dan SNR 𛾠= 15 ð‘‘ðµ untuk polar codes. Hasil menunjukkan bahwa penambahan channel coding mampu menangkap diversity order kedua dan performansi polar codes lebih baik dibandingkan dengan QC-LDPC. Kata kunci: 5G, BPSK, OFDM, Polar, QC-LDPC  ABSTRACT The 5G network has become a significant milestone in the evolution of wireless technology, offering remarkable speed and performance to meet the growing demands of connectivity. In the 5G network, channel coding is a crucial element to ensure reliable and efficient data transmission. This research evaluate the 5G network operating at a frequency of 26 GHz and a bandwidth of 200 MHz, utilizing Orthogonal Frequency Division Multiplexing (OFDM) with an Fast Fourier Transform (FFT) size of 256 and Binary Phase Shift Keying (BPSK) modulation. The research evaluates the comparison of adding channel coding using QC-LDPC and polar codes. The performance of QC-LDPC codes at a bit error rate (BER) of 10-4 can be achieved with an SNR of 𛾠= 17 ð‘‘ðµ for QC-LDPC codes and an SNR of 𛾠= 15 ð‘‘ðµ for polar codes. The results shows the addition of channel coding is capable of capturing second-order diversity, and polar codes outperforms QC-LDPC in terms of performances. Keywords: 5G, BPSK, OFDM, Polar, QC-LDPC

IntroductionThe Arctic sea ice extent in September (when it is at its lowest) has declined 13% Q10 per decade, and the Arctic Ocean is becoming a more Atlantic-influenced system. Rapid climate-forced changes are taking place in many high-latitude marine ecosystems. The Barents Sea is one such high-latitude shelf ecosystem, between approximately 70° and 80°N in the Norwegian Arctic. The purpose of the current study was to estimate zoobenthic blue carbon across multiple habitats within the Barents Sea (trough, basin, shelf, and shallows), potentially providing values to aid ecosystem-based management of these areas under future climate change scenarios.MethodWe tested this by capture and analysis of 947 high-resolution (each 405.7 × 340.6 mm, 12 MB, 5 megapixels) seabed images at 17 sites with latitudinal cline, linked to a collection of corresponding oceanographic data. Biotas within these images were identified to one of the 14 functional groups and the density was calculated. Mean stored carbon per individual was assigned by ash mass (AM) and ash-free dry mass (AFDM) of individuals caught within Agassiz trawl deployments at the same sites.ResultsTrough sites, except for one site (B16), have a low quantity of zoobenthic blue carbon compared with the shallow, shelf, and basin habitats.DiscussionThe results of a previous study focused entirely on trough habitats and are therefore difficult to scale up as the basis for a meaningful estimate of across-habitat zoobenthic blue carbon in the Barents Sea. Compared with the trough and the basin, the shelf and shallow habitats of the Barents Sea are also subjected to more trawling events through demersal fisheries and showed higher zoobenthic blue carbon stock values.

The affect of temperature on tissue protein synthesis rates has been reported in temperate and tropical, but not Antarctic fishes. Previous studies have generally demonstrated low growth rates in Antarctic fish species in comparison to temperate relatives and elevated levels of protein turnover. This study investigates how low temperatures effect tissue protein synthesis and hence tissue growth in a polar fish species. Groups of Antarctic, Harpagifer antarcticus and temperate, Lipophrys pholis , were acclimated to a range of overlapping water temperatures and protein synthesis was measure in white muscle (WM), liver and gastrointestinal tract (GIT). WM protein synthesis rates increased linearly with temperature in both species (H. antarcticus 0.16–0.23%.d−1, L. pholis , 0.31–0.76%.d−1), while liver (H. antarcticus 0.24–0.27%.d−1, L. pholis , 0.44–1.03%.d−1) and GIT were unaffected by temperature in H. antarcticus but increased non-linearly in L. pholis (H. antarcticus 0.22–0.26%.d−1, L. pholis , 0.40–0.86%.d−1). RNA to protein ratios were unaffected by temperature in H. antarcticus but increased weakly, in L. pholis WM and liver. In L. pholis , RNA translational efficiency increased significantly with temperature in all tissues, but only in liver in H. antarcticus. At the overlapping temperature of 3 °C, protein synthesis (WM 26%, Liver, 39%, GIT, 35%) and RNA translational efficiency (WM 273%, Liver, 271%, GIT, 300%) were significantly lower in H. antarcticus than L. pholis , while RNA to protein ratios were significantly higher (WM 270%, Liver 170%, GIT 186%). Tissue specific effects of temperature are detectable in both species. This study provides the first evidence, that tissue protein synthesis rates are constrained in Antarctic fishes. [Display omitted] • At 3 °C protein synthesis rates were significantly lower in Antarctic than temperate fishes. • RNA to protein ratios were significantly higher in Antarctic than temperate fishes. • RNA translational efficiencies were significantly lower in Antarctic than temperate fishes. • Preliminary evidence suggest protein synthesis is constrained at polar water temperatures. [ABSTRACT FROM AUTHOR]

Circadian rhythms synchronize the internal physiology of animals allowing them to anticipate daily changes in their environment. Arctic habitats may diminish the selective advantages of circadian rhythmicity by relaxing daily rhythmic environmental constraints, presenting a valuable opportunity to study the evolution of circadian rhythms. In reindeer, circadian control of locomotor activity and melatonin release is weak or absent, and the molecular clockwork is reportedly non-functional. Here we present new evidence that the circadian clock in cultured reindeer fibroblasts is rhythmic and temperature-compensated. Compared with mouse fibroblasts, however, reindeer fibroblasts have a short free-running period, and temperature cycles have an atypical impact on clock gene regulation. In reindeer cells, Per2 and Bmal1 reporters show rapid responses to temperature cycles, with a disintegration of their normal antiphasic relationship. The antiphasic Per2-Bmal1 relationship re-emerges immediately after release from temperature cycles, but without complete temperature entrainment and with a marked decline in circadian amplitude. Experiments using Bmal1 promoter reporters with mutated RORE sites showed that a reindeer-like response to temperature cycles can be mimicked in mouse or human cell lines by decoupling Bmal1 reporter activity from ROR/REV-ERB-dependent transcriptional regulation. We suggest that weak coupling between core and secondary circadian feedback loops accounts for the observed behavior of reindeer fibroblasts in vitro. Our findings highlight diversity in how the thermal environment affects the temporal organization of mammals living under different thermoenergetic constraints., Competing Interests: Conflict of Interest StatementThe authors have no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Biocrusts are crucial components of Arctic ecosystems, playing significant roles in carbon and nitrogen cycling, especially in regions where plant growth is limited. However, the microbial communities within Arctic biocrusts and their strategies for surviving the harsh conditions remain poorly understood. In this study, the microbial profiles of Arctic biocrusts across different seasons (summer, autumn, and winter) were investigated in order to elucidate their survival strategies in extreme conditions. Metagenomic and metatranscriptomic analyses revealed significant differences in microbial community composition among the sites located in different elevations. The bacterial communities were dominated by Actinobacteria and Proteobacteria, while the fungal communities were mainly represented by Ascomycota and Basidiomycota, with lichenized and saprotrophic traits prevailing. Cyanobacteria were primarily composed of heterocystous cyanobacteria. Furthermore, the study identified molecular mechanisms underlying cold adaptation, including the expression of heat shock proteins and cold-inducible RNA helicases in cyanobacteria and fungi. Overall, the microbial communities appear to be permanently well adapted to the extreme environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

In this work, the derivation of a general expression for the residual entropy for quasi-chemical models – including modern COSMO-RS/SAC – is shown. This expression is equivalent to equations that had to be assumed or postulated in previous works. More interestingly, it allows to unravel order (or non-randomness) in pure compounds and mixtures in a very detailed way. It is possible to investigate the entropic contribution of every possible pair of molecular surface segments, without relying on any lattice or coordination number. Different types of mixtures are very well explained by modern quasi-chemical models, including polar, apolar, and associating compounds showing positive, negative, and s-shaped excess entropy. Finally, it is shown that these models are unable to precisely represent some aqueous mixtures — the assumption of pairwise additive interactions is apparently too limited in those cases. [Display omitted] [ABSTRACT FROM AUTHOR]

• The real-time single-frequency precise point positioning technique was evaluated for the first time in the Arctic, and Antarctic based on real experimental data. • The ionosphere-free single-frequency precise point positioning approach was investigated for the first time in Actic and Antarctic, considering all possible auroral activities. • The ionosphere-free single-frequency precise point positioning technique is not affected by ionospheric scintillations. • The real-time ionosphere-free single-frequency precise point positioning technique can be reliably employed for real-time navigation applications both arctic and Antarctic polar regions. This contribution presents an evaluation of the positioning ability of the real-time (RT) ionosphere-free (IF) single-frequency precise point positioning (SF-PPP) technique in Arctic and Antarctic under different auroral activities. Firstly, Global Positioning System (GPS)-only observations obtained from International GNSS Service (IGS) stations in the Arctic were evaluated with RT IF SF-PPP under all possible auroral activities. Then, a series of kinematic experiments were conducted using a zodiac boat on Livingston Island, located on the Antarctic Peninsula, under different auroral activities. Observations from the kinematic experiments were also evaluated using the RT IF SF-PPP. The outcomes indicate that the IF SF-PPP approach is not affected by ionospheric activities. Furthermore, the results reveal that the RT IF SF-PPP provides dm- and m-level positioning accuracy for horizontal and vertical components, respectively. The findings demonstrate that the RT IF SF-PPP technique can be reliably employed in real-time navigation applications in the Arctic and Antarctic. [ABSTRACT FROM AUTHOR]

The family of polar hybrid perovskites, in which bulk photovoltaic effects (BPVEs) drive steady photocurrent without bias voltage, have shown promising potentials in self-powered polarization-sensitive photodetection. However, reports of BPVEs in 3D perovskites remain scare, being mainly hindered by the limited dipole moment or lack of symmetry breaking. Herein, a polar 3D perovskitoid, (BDA)Pb 2 Br 6 (BDA = NH 3 C 4 H 8 NH 3 ), where the spontaneous polarization (P s )-induced BPVE drives self-powered photodetection of polarized-light is reported. Emphatically, the edge-sharing Pb 2 Br 10 dimer building unit allows the optical anisotropy and polarity in 3D (BDA)Pb 2 Br 6 , which triggers distinct optical absorption dichroism ratio of ≈2.80 and BPVE dictated photocurrent of 3.5 µA cm -2 . Strikingly, these merits contribute to a polarization-sensitive photodetection with a high polarization ratio (≈4) under self-powered mode, beyond those of 2D hybrid perovskites and inorganic materials. This study highlights the potential of polar 3D perovskitoids toward intelligent optoelectronic applications., (© 2024 Wiley‐VCH GmbH.)

We report a study on the stability, optical absorption and modulated electronic properties of the ZnO(0001-) and MoS 2 Van der Waals heterostructure using density functional theory. We employed a supercell of ZnO/MoS 2 hybrid and specifically explored the effects of creating an interface with the O-terminated face of ZnO while considering the interlayer interaction. We observed an increase in the band gap opening of MoS 2 within the hybrid structure (1.37 eV) is primarily attributed to in-plane strain, with minimal contribution from the identified charge transfer occurring from MoS 2 to ZnO. Notably, the hybrid structure exhibits enhanced photo absorption in the visible and near-infrared regions, highlighting their significance for optoelectronic applications., (© 2024 IOP Publishing Ltd.)

Heart rate variability (HRV) is used as a measure of autonomic nervous system (ANS) function and is based on heart rate (HR) beat-to-beat time interval variance analysis. Various techniques are used for recording HR, however, few studies have compared Holter-type recordings vs HR monitors (HRM) during an orthostatic challenge., Objectives: Compare HRV measures from an electrocardiogram (ECG) Holter and a HRM as a tool for investigating ANS response for post-concussion rehabilitation follow-up., Methods: Twenty-seven participants ( n = 27; 15 females, 12 males), 18 to 35 years old, non-smoking, no history of cardiac illness and physically active (3 times per week, 60 mins, moderate intensity exercise) participated in the study. ECG signals and HRM were recorded beat-to-beat (R-R) simultaneously. A motorized tilt table was set at 0 degree for supine and 85 degrees for standing position. Participants were instructed to remain for 7 minutes in each position. R-R signals from both Holter and Polar HRM recording starting points were matched before further analysis. Bland-Altman plots were used to compare recordings from the Holter (gold standard) and the Polar HRM in both positions. Unpaired t -test was used to compare measurements obtained with both systems. Significance was set at p < 0.05., Results: No significant differences were observed between R-R measurements taken with both systems under equal conditions (supine and standing). Same variables under similar conditions were significantly correlated ( p = 0.0001)., Conclusion: Both recording and analysis systems (Holter vs HRM) yielded comparable results. Thus, both systems appear valid and interchangeable for HRV analysis for measuring orthostatic challenge HRV responses.

Planning of mission toward the lunar polar region is supported here by the analysis and better understanding of the most frequent landforms: craters on the Moon in the polar region between 79.30 and 84.35 southern latitude. This work surveys impact crater morphologies and spatial density based age estimation and slopes for eight earlier selected, large candidate landing regions of the Luna-27 solar powered ice drilling mission at the southern lunar polar region. The morphological, morphometrical, slope and dating analysis provided the following results: The d/D values of craters follow the earlier found d/D trend for larger craters, but there is a scatter in depth values related to the ageing of craters. The occurrence of shallow craters looks to be somewhat more abundant here than at lower lunar latitudes, in agreement with Mahanti et al. (2015). Beside fresh craters, rock boulders also occur at some km sized local topographic elevations, indicating erosion of ∼1 m thick regolith layer by micro-scale impacts roughly on the scale of 100 Ma. Characteristic temporal sequence of change in the morphology of about 100 m-sized craters confirmed earlier results. The sequence starts from the freshest craters, with mass wasting produced stripes in the interior slope, later diminish of high-reflectance proximal ejecta happens, then boulders, and even later elevated rims diminish. The surveyed large terrains showed crater statistics-derived model ages ranged between 3.9 and 4.2 Ga, indicating below a thin pulverised surface regolith layer, the topography of the poorly fragmented bedrock below it still holds the Late Heavy Bombardment aged basement. The equilibrium crater population was possibly identified below the 100–200 m diameter range. Surveying crater retention at >30° slopes indicates exposure of 78–140 Ma for steep terrains, and 330–150 Ma for flat <5° slope surfaces considering the size domain below 100 m diameter. This observation indicates rejuvenation of the top few m thin layer of slopes produces faster mixing than on plains. The surveyed kilometre sized craters formed about 1–2 Ga ago, and show correlation between formation age and depth, indicating an infilling rate around 100 m thickness in 1 Ga duration. This is 2 orders of magnitude larger than the 1–2 m impact driven regolith mixing depth during the same period. Thus, while impact mixing desiccates the shallow top regolith layer, inside km scale craters earlier accumulated ice might still be there shielded by faster rock debris accumulation. The surveyed candidate landing regions were evaluated according to general landing safety, lower temperature (to support ice preservation), and solar illumination (for energy supply). Comparing the eight regions, altogether 5.1% of their total area was found to meet with the threshold values of slope angle below 8°, modelled 1 m deep subsurface temperature below 125 K and at least 20% of time available solar illumination and Earth visibility. The largest continuous area that fulfil the used constraints are present in the candidate LS8 area at −82.70°, −82.72°. • Lunar surface morphology was analysed at 8 candidate polar landing areas. • The survey supports the characterization of possible ice hosting sites. • Boulder fields and fresh rayed craters' observability were characterised. • Crater shallowing by ageing was linked to characteristic morphological states. • Km sized craters infilled at larger than regolith mixing depth, might preserve ice. [ABSTRACT FROM AUTHOR]

The late nineteenth and early twentieth century saw dramatic new developments in climatic medicine, particularly the institutionalisation of thinking about tropical hygiene. There were also more limited efforts to understand how hygiene theories should be applied in a polar environment. Studying the British National Antarctic Expedition (1901-1904), led by Robert Falcon Scott, helps us understand how these practices had both similarities and differences from applications of hygiene in other contexts. The expedition offers unique insights into debates about hygiene, environment, and health because of the important, and well documented, role that medics, naval officers and scientists played in organising logistical arrangements for the journey to Antarctica. In analysing the writings of expedition members and organisers, this paper examines the ways that the universal tools of hygiene theories were applied and developed in a polar environment. Many of the most acute threats seemed to come not from the outside environment but from the explorers' supplies and equipment. There was general agreement on many issues. Yet the expedition's organisers, medics and leadership had numerous arguments about the best way to preserve or restore health. These disagreements were the product of both competing medical theories about the cause of disease and the importance of embodied (and somewhat subjective) observations in establishing the safety of foods, atmospheres and environments in this period.

The infection cycle of phage λ terminates in lysis mediated by three types of lysis proteins, each disrupting a layer in the bacterial envelope: the S105 holin, the R endolysin, and the Rz/Rz1 spanin complex targeting the inner membrane, cell wall or peptidoglycan, and the outer membrane, respectively. Video microscopy has shown that in most infections, lysis occurs as a sudden, explosive event at a cell pole, such that the initial product is a less refractile ghost that retains rod-shaped morphology. Here, we investigate the molecular basis of polar lysis using time-lapse fluorescence microscopy. The results indicate that the holin determines the morphology of lysis by suddenly forming two-dimensional rafts at the poles about 100 s prior to lysis. Given the physiological and biochemical similarities between the lambda holin and other class I holins, dynamic redistribution and sudden concentration may be common features of holins, probably reflecting the fitness advantage of all-or-nothing lysis regulation.IMPORTANCEIn this study, we use fluorescent video microscopy to track -green fluorescent protein (GFP)-labeled holin in the minutes prior to phage lysis. Our work contextualizes prior genetic and biochemical data, showing when hole formation starts and where holin oligomers form in relation to the site of lytic rupture. Furthermore, prior work showed that the morphology of lambda-infected cells is characterized by an explosive event starting at the cell pole; however, the basis for this was not clear. This study shows that holin most often oligomerizes at cell poles and that the site of the oligomerization is spatially correlated with the site of lytic blowout. Therefore, the holin is the key contributor to polar lysis morphology for phage lambda., Competing Interests: The authors declare no conflict of interest.