bluuebunny/crossref_metadata_2025 huggingface dataset:
Random pinhole attenuator for high-power laser beams
Authors: Park Seong Cheol , Yun Hyeok , Yoon Jin Woo , Lee Seong Ku , Sung Jae Hee , Choi Il Woo , Nam Chang Hee , Kim Kyung Taec
Published: April 2024

The intensity attenuation of a high-power laser is a frequent task in the measurements of optical science. Laser intensity can be attenuated by inserting an optical element, such as a partial reflector, polarizer or absorption filter. These devices are, however, not always easily applicable, especially in the case of ultra-high-power lasers, because they can alter the characteristics of a laser beam or become easily damaged. In this study, we demonstrated that the intensity of a laser beam could be effectively attenuated using a random pinhole attenuator (RPA), a device with randomly distributed pinholes, without changing the beam properties. With this device, a multi-PW laser beam was successfully attenuated and the focused beam profile was measured without any alterations of its characteristics. In addition, it was confirmed that the temporal profile of a laser pulse, including the spectral phase, was preserved. Consequently, the RPA possesses significant potential for a wide range of applications.
New grating compressor designs for XCELS and SEL-100 PW projects
Authors: Khazanov Efim
Published: April 2024

The problem of optimizing the parameters of a laser pulse compressor consisting of four identical diffraction gratings is solved analytically. The goal of optimization is to obtain maximum pulse power, completely excluding both beam clipping on gratings and the appearance of spurious diffraction orders. The analysis is carried out in a general form for an out-of-plane compressor. Two particular ‘plane’ cases attractive from a practical point of view are analyzed in more detail: a standard Treacy compressor (TC) and a compressor with an angle of incidence equal to the Littrow angle (LC). It is shown that in both cases the LC is superior to the TC. Specifically, for 160-cm diffraction gratings, optimal LC design enables 107 PW for XCELS and 111 PW for SEL-100 PW, while optimal TC design enables 86 PW for both projects.
Development of an ultrathin liquid sheet target for laser ion acceleration at high repetition rates in the kilohertz range
Authors: Füle M. , Kovács A. P. , Gilinger T. , Karnok M. , Gaál P. , Figul S. , Marowsky G. , Osvay K.
Published: April 2024

A colliding microjet liquid sheet target system was developed and tested for pairs of round nozzles of 10, 11 and 18 μm in diameter. The sheet’s position stability was found to be better than a few micrometers. Upon interaction with 50 mJ laser pulses, the 18 μm jet has a resonance amplitude of 16 μm at a repetition rate of 33 Hz, while towards 100 Hz it converges to 10 μm for all nozzles. A white-light interferometric system was developed to measure the liquid sheet thickness in the target chamber both in air and in vacuum, with a measurement range of 182 nm–1 μm and an accuracy of ±3%. The overall shape and 3D shape of the sheet follow the Hasson–Peck model in air. In vacuum versus air, the sheet gradually loses 10% of its thickness, so the thinnest sheet achieved was below 200 nm at a vacuum level of 10–4 mbar, and remained stable for several hours of operation.
Laminar boundary layer separation and reattachment on a rotating sphere
Authors: Smith Benjamin J. , Hussain Z. , Calabretto S.A.W. , Garrett S.J.
Published: April 2024

A new model of the steady boundary layer flow around a rotating sphere is developed that includes the widely observed collision and subsequent eruption of boundary layers at the equator. This is derived following the Segalini & Garrett (J. Fluid Mech., vol. 818, 2017, pp. 288–318) asymptotic approach for large Reynolds numbers but replacing the Smith & Duck (Q. J. Mech. Appl. Maths, vol. 30, issue 2, 1977, pp. 143–156) correction with a higher-order version of the Stewartson (Grenzschichtforschung/Boundary Layer Research, 1958, pp. 59–71. Springer) model of the equatorial flow. The Stewartson model is then numerically solved, for the first time, via a geometric multigrid method that solves the steady planar Navier–Stokes equations in streamfunction-vorticity form on large rectangular domains in a quick and efficient manner. The results are then compared with a direct numerical simulation of the full unsteady problem using the Semtex software package where it is found that there is broad qualitative agreement, namely the separation and reattachment of the boundary layer at the equator. However, the presence of unobserved behaviour such as a large area of reverse flow seen at lower Reynolds numbers than those observed in other studies, and that the absolute error increases with Reynolds number suggest the model needs improvement to better capture the physical dynamics.
Numerical study of a viscous breaking water wave and the limit of vanishing viscosity
Authors: Riquier Alan , Dormy Emmanuel
Published: April 2024

We introduce a numerical strategy to study the evolution of two-dimensional water waves in the presence of a plunging jet. The free-surface Navier–Stokes solution is obtained with a finite, but small, viscosity. We observe the formation of a surface boundary layer where the vorticity is localised. We highlight convergence to the inviscid solution. The effects of dissipation on the development of a singularity at the tip of the wave is also investigated by characterising the vorticity boundary layer appearing near the interface.
Dense turbulent suspensions at a liquid interface
Authors: Shin Seunghwan , Coletti Filippo
Published: April 2024

The nexus between turbulence, particle interaction and interfacial tension is virtually unexplored, despite being highly relevant to a wealth of industrial and environmental settings. Here we investigate it by conducting experiments on non-Brownian spherical particles at the interface of turbulent liquid layers. The latter are electromagnetically stirred in a quasi-two-dimensional apparatus, while the particles are individually tracked. By systematically varying interfacial conditions, turbulence intensity, particle size and concentration from dilute to dense, we map the system behaviour over a wide parameter space. We reveal how the dynamics is governed by the balance of drag, capillarity and lubrication. Based on their scaling, we propose a phase diagram comprising three distinct regimes, characterized by widely different levels of clustering and fluctuating energy of the particles. This is quantitatively confirmed by the experimental results.
Terminus thinning drives recent acceleration of a Greenlandic lake-terminating outlet glacier
Authors: Holt Ed , Nienow Peter , Medina-Lopez Encarni
Published: April 2024

Ice-contact proglacial lakes affect ice dynamics and the transition of glacier termini from land- to lake-terminating has been shown to cause ice flow acceleration. In recent decades, the number and size of Greenlandic ice-marginal lakes has increased, highlighting the need to further understand these lake-terminating ice-margins as their influence on ice sheet mass balance increases. Here, time series of satellite-derived observations of ice velocity, surface elevation, and terminus position were generated at a lake-terminating outlet glacier, Isortuarsuup Sermia, and the nearby land-terminating Kangaasarsuup Sermia in south-west Greenland. At Isortuarsuup Sermia, annual surface velocity at the terminus increased by a factor of 2.5 to 214 ± 4 m yr−1 (2013–2021), with the magnitude of this acceleration declining with distance up-glacier. Meanwhile, near-terminus surface elevation changed at a rate of −2.3 ± 1.1 m yr−1 (2012–2021). Conversely, velocity change at Kangaasarsuup Sermia was minimal, while surface elevation change was approximately half at comparable elevations (−1.2 ± 0.3 m yr−1). We attribute these dynamic differences to thinning at Isortuarsuup Sermia and subsequent retreat from a stabilising sublacustrine moraine, and emphasise the potential of proglacial lakes to enhance future rates of mass loss from the Greenland Ice Sheet.
Law and scale: lessons from Northern Ireland and Brexit
Authors: de Mars Sylvia , O'Donoghue Aoife
Published: April 2024

All aspects of law possess scaler elements, but critiques from the ‘politics of scale’, a concept well established in political geography, remain rare in legal analysis. Brexit, especially as regards Northern Ireland, provides a key opportunity to consider scaler analysis both in a descriptive and theoretical sense. Scale deepens our understanding of how law co-constitutes multiple scales but also highlights where a flat understanding of law tied to vertical jurisdictional frames foils attempts to garner a full understanding of its operation. Northern Ireland, a legal and political space that from one perspective lends itself to an apparently clear-cut vertical description of legal scales, actually presents a rich space where networked, rhetorical and nodular scales and structures continuously (re)contest scaled solutions. The Brexit outcome of what used to be known as the Protocol on Ireland/Northern Ireland and is now known as the Windsor Framework – and specifically how the Framework is intended to operate in practice – provides an opportunity to not only understand Northern Ireland within a scale and law frame, but also to highlight the shortcomings of law's traditional scaler approach and what lessons may be learned when analysing or engaging with the intersection of law and politics in similar future situations.
Professors of racial medicine: imperialism and race in nineteenth-century United States medical schools
Authors: Willoughby Christopher D. E.
Published: April 2024

This article examines some of the racist features of nineteenth-century medical school curricula in the United States and the imperial networks necessary to acquire the data and specimens that underpinned this part of medical education, which established hierarchies between human races and their relationship to the natural environment. It shows how, in a world increasingly linked by trade and colonialism, medical schools were founded in the United States and grew as the country developed its own imperial ambitions. Taking advantage of the global reach of empires, a number of medical professors in different states, such as Daniel Drake, Josiah Nott and John Collins Warren, who donated his anatomical collection to Harvard Medical School on his retirement in 1847, began to develop racial theories that naturalised slavery and emerging imperialism as part of their medical teaching.
A proposal for an updated and revised stratigraphical framework of the Miocene in the Achterhoek (eastern Netherlands)
Authors: Munsterman Dirk K. , Van den Bosch Maarten , Wesselingh Frank P. , Helwerda Marian , Busschers Freek S.
Published: April 2024

The comprehensive overview of Neogene lithostratigraphy in the eastern Netherlands dates back to the mid-1970s. In the present study, continuous gamma-ray logs and in situ sediment core samples from six boreholes in the area allowed palynological and mollusc analyses and wireline log-based correlation. These investigations were aimed at updating and revising the existing Neogene lithostratigraphy within the Stratigraphic Nomenclature of the Netherlands by integrating litho-, bio-, and sequence-stratigraphic approaches. The analytical results yielded the establishment of new holo- and lectostratotype sections, together with cross-border interregional correlation. The lithostratigraphic revision resulted in the modified definition of the Aalten, Eibergen and Delden members and the definition of two new proposed members: the Dale and Doetinchem members. The Ticheloven bed, removed in earlier studies, is proposed to be reinstated, and the Stemerdink Bed is upgraded in its hierarchical status to the Stemerdink member. All lithostratigraphic units are included in the present Miocene subdivision of the Groote Heide and Diessen formations, which include three recognisable unconformities: the Early-Miocene Unconformity (EMU), Mid-Miocene Unconformity (MMU) and Late-Miocene Unconformity (LMU). The new, revised, reintroduced and existing local lithostratigraphic units and sequences are discussed with their counterparts in the south and southeast of the Netherlands, in Germany and Belgium, and from this a regionally consistent framework has emerged of the regional Neogene lithostratigraphy.
Evolutionary Map of the Universe (EMU): A pilot search for diffuse, non-thermal radio emission in galaxy clusters with the Australian SKA Pathfinder
Authors: Duchesne S.W. , Botteon A. , Koribalski B.S. , Loi F. , Rajpurohit K. , Riseley C.J. , Rudnick L. , Vernstrom T. , Andernach H. , Hopkins A.M. , Kapinska A.D. , Norris R.P. , Zafar T.
Published: April 2024

Clusters of galaxies have been found to host Mpc-scale diffuse, non-thermal radio emission in the form of central radio halos and peripheral relics. Turbulence and shock-related processes in the intra-cluster medium are generally considered responsible for the emission, though details of these processes are still not clear. The low surface brightness makes detection of the emission a challenge, but with recent surveys with high-sensitivity radio telescopes we are beginning to build large samples of these sources. The Evolutionary Map of the Universe (EMU) is a Southern Sky survey being performed by the Australian SKA Pathfinder (ASKAP) over the next few years and is well-suited to detect and characterise such emission. To assess prospects of the full survey, we have performed a pilot search of diffuse sources in 71 clusters from the Planck Sunyaev–Zeldovich (SZ) cluster catalogue (PSZ2) found in archival ASKAP observations. After re-imaging the archival data and performing both (u, v)-plane and image-plane angular scale filtering, we detect 21 radio halos (12 for the first time, excluding an additional six candidates), 11 relics (in seven clusters, and six for the first time, excluding a further five candidate relics), along with 12 other, unclassified diffuse radio sources. From these detections, we predict the full EMU survey will uncover up to

$\approx 254$

radio halos and

$\approx 85$

radio relics in the 858 PSZ2 clusters that will be covered by EMU. The percentage of clusters found to host diffuse emission in this work is similar to the number reported in recent cluster surveys with the LOw Frequency ARray (LOFAR) Two-metre Sky Survey [Botteon, et al. 2022a, A&A, 660, A78], suggesting EMU will complement similar searches being performed in the Northern Sky and provide us with statistically significant samples of halos and relics at the completion of the full survey. This work presents the first step towards large samples of the diffuse radio sources in Southern Sky clusters with ASKAP and eventually the SKA.
RG-CAT: Detection pipeline and catalogue of radio galaxies in the EMU pilot survey
Authors: Gupta Nikhel , Norris Ray P. , Hayder Zeeshan , Huynh Minh , Petersson Lars , Rosalind Wang X. , Hopkins Andrew M. , Andernach Heinz , Gordon Yjan , Riggi Simone , Yew Miranda , Crawford Evan J. , Koribalski Bärbel , Filipović Miroslav D. , Kapińska Anna D. , Shabala Stanislav , Vernstrom Tessa , Marvil Joshua R.
Published: April 2024

We present source detection and catalogue construction pipelines to build the first catalogue of radio galaxies from the 270$\rm deg^2$pilot survey of the Evolutionary Map of the Universe (EMU-PS) conducted with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The detection pipeline uses Gal-DINO computer vision networks (Gupta et al. 2024, PASA, 41, e001) to predict the categories of radio morphology and bounding boxes for radio sources, as well as their potential infrared host positions. The Gal-DINO network is trained and evaluated on approximately 5 000 visually inspected radio galaxies and their infrared hosts, encompassing both compact and extended radio morphologies. We find that the Intersection over Union (IoU) for the predicted and ground-truth bounding boxes is larger than 0.5 for 99% of the radio sources, and 98% of predicted host positions are within$3^{\prime \prime}$of the ground-truth infrared host in the evaluation set. The catalogue construction pipeline uses the predictions of the trained network on the radio and infrared image cutouts based on the catalogue of radio components identified using theSelavysource finder algorithm. Confidence scores of the predictions are then used to prioritiseSelavycomponents with higher scores and incorporate them first into the catalogue. This results in identifications for a total of 211 625 radio sources, with 201 211 classified as compact and unresolved. The remaining 10 414 are categorised as extended radio morphologies, including 582 FR-I, 5 602 FR-II, 1 494 FR-x (uncertain whether FR-I or FR-II), 2 375 R (single-peak resolved) radio galaxies, and 361 with peculiar and other rare morphologies. Each source in the catalogue includes a confidence score. We cross-match the radio sources in the catalogue with the infrared and optical catalogues, finding infrared cross-matches for 73% and photometric redshifts for 36% of the radio galaxies. The EMU-PS catalogue and the detection pipelines presented here will be used towards constructing catalogues for the main EMU survey covering the full southern sky.
Torsion in classifying spaces of gauge groups
Authors: Kameko Masaki
Published: April 2024

We determine when the integral homology of the classifying space of a

$PU(n)$

-gauge group over the sphere

$S^2$

has torsion.
Skew group categories, algebras associated to Cartan matrices and folding of root lattices
Authors: Chen Xiao-Wu , Wang Ren
Published: April 2024

For an action of a finite group on a finite EI quiver, we construct its ‘orbifold’ quotient EI quiver. The free EI category associated to the quotient EI quiver is equivalent to the skew group category with respect to the given group action. Specializing the result to a finite group action on a finite acyclic quiver, we prove that, under reasonable conditions, the skew group category of the path category is equivalent to a finite EI category of Cartan type. If the ground field is of characteristic

$p$

and the acting group is a cyclic

$p$

-group, we prove that the skew group algebra of the path algebra is Morita equivalent to the algebra associated to a Cartan matrix, defined in [C. Geiss, B. Leclerc, and J. Schröer, Quivers with relations for symmetrizable Cartan matrices I: Foundations, Invent. Math. 209 (2017), 61–158]. We apply the Morita equivalence to construct a categorification of the folding projection between the root lattices with respect to a graph automorphism. In the Dynkin cases, the restriction of the categorification to indecomposable modules corresponds to the folding of positive roots.
The West German and Italian Left in the “Two Cultures” Debate: Trasnationalization and Localization (1964–1969)
Authors: Costa Ettore
Published: April 2024

This article delves into the transnational aspects of the “Two Cultures” debate initiated by the British chemist and writer C. P. Snow, and explores how Italian and West German intellectuals localized and translated aspects of the debate within their respective political landscapes. Snow described the relationship between science and the humanities, and attributed a unique social responsibility to science. Prominent leftist thinkers, including Gino Martinoli, Adriano Buzzati Traverso, Aldo Visalberghi, Giulio Preti, Pier Paolo Pasolini, Karl Steinbuch, Hans Mohr, Hilde Domin, Jürgen Habermas, and Robert Jungk, engaged Snow's ideas, each formulating their stance on the role of science. These intellectuals were divided in their response. Some concurred with Snow, viewing scientific advancement as a cornerstone of social progress and considering the scientific ethos as a model for political emulation. Others, however, were critical, questioning the very notions of scientific progress, rationality, and modernization. This intellectual discourse foreshadowed the New Left's critique of scientism in the 1970s, a movement that significantly challenged the longstanding marriage between socialism and science.
Hyper-exegesis in Persian translations of the Qu'ran: On the Disjointed Letters as Translational Challenges
Authors: Tahmasebian Kayvan , Gould Rebecca Ruth
Published: April 2024

Although translation and commentary are often treated as distinct, separable activities in literary and intellectual history, the Persian tradition of Qur'an exegesis demonstrates that they are best understood in relation to each other. Introducing the concept of hyper-exegesis as a mode of interpretation that approximates translation, we examine the dialectical relationship between translation and commentary by focusing on how Persian exegetes have dealt with the so-called “disjointed letters” (ḥurūf muqaṭaʿāt). The disjointed letters inaugurate twenty-nine chapters (sūras) of the Qur'an. We show how six Persian translator-exegetes (the anonymous author of Tarjama-yi Tafsir-I Tabari, Isfarayini, Surabadi, Nasafi, Maybudi, and Razi) used commentary in response to their understanding of the Qur'an's inimitability. Persian translators’ confrontation with the disjointed letters are presented here as a case study of the ways in which translatability and commentary overlap and enrich each other. As a contribution to translation studies and literary theory, this research reveals how untranslatability is situated at the core of the translational enterprise, and how commentary functions as a mode of translating the ineffable.
Macroeconomic Expectations and Expected Returns
Authors: Deng Yizhe , Wang Yunqi , Zhou Ti
Published: April 2024

Using the macroeconomic forecasts of professional economists, we construct a comprehensive macro condition index that summarizes subjective expectations of output, inflation, and labor and housing market conditions. The index predicts stock returns and produces countercyclical equity premium forecasts, both in- and out-of-sample. Our results contrast with the procyclical subjective equity premia documented in recent literature. We show that the index reflects the true but unobserved macroeconomic condition that impacts the equity premium. Moreover, the predictability is not affected by belief biases and operates via a discount rate channel. The index’s predictability conforms to an explanation based on time-varying risk premia.
A framework for understanding the contributions of local residents to protected area law enforcement
Authors: Sharkey William , Milner-Gulland E.J. , Sinovas Pablo , Keane Aidan
Published: April 2024

Terrestrial and marine protected areas have long been championed as an approach to biodiversity conservation. For protected areas to be effective, equitable and inclusive, the involvement of local residents in their management and governance is considered important. Globally, there are many approaches to involving local residents in protected area law enforcement. However, opportunities for comparing different approaches have been limited by the lack of a clear common framework for analysis. To support a more holistic understanding, we present a framework for analysing the contributions of local residents to protected area law enforcement. Informed by a review of the literature and discussions with conservation practitioners, the framework comprises five key dimensions: (1) the different points in the enforcement system at which local residents are involved, (2) the nature of local participation in decision-making, (3) the type of external support provided to local residents, (4) the different motivating forces for participation, and (5) the extent to which local participation is formalized. We apply the framework to three real-world case studies to demonstrate its use in analysing and comparing the characteristics of different approaches. We suggest this framework could be used to examine variation in local participation within the enforcement system, inform evaluation and frame constructive discussions between relevant stakeholders. With the global coverage of protected areas likely to increase, the framework provides a foundation for better understanding the contributions of local residents to protected area law enforcement.
SEATON SNOOK AND THE BUILDING OF A PARAFICTIONAL SEASIDE TOWN
Authors: Falconer Peter
Published: April 2024

Seaton Snook was a thriving community of fishermen, blacksmiths, teachers, seacoalers, labourers and musicians on the coast of County Durham, UK. After 1968, however, government records and newspaper reports referring to the town cease and there are, apparently, no former residents still living. This article outlines the creation of What Happened to Seaton Snook?, an internet-based archive of sounds and music from the area, its residents and its workers, devised to try and form a picture of the town and what happened there. Among the nearly 100 artefacts in this ethnomusicological study are pieces for piano and harpsichord, pedagogic works, folk tunes for voice and Northumbrian smallpipes, brass band music, Krautrock, psychedelic rock and works for magnetic tape. There are biographies and photographs of people key to the history of the town, and interviews with experts in matters pertaining to the artefacts. The archive also seeks to examine the economic and cultural neglect of the North East of England and the importance of the stories we tell around the music we make.
Water and Chlorine in the Martian Subsurface Along the 27 km Traverse of NASA's Curiosity Rover According to DAN Measurements: 2. Results for Distinct Geological Regions
Authors: Nikiforov S. Y. , Djachkova M. V. , Gellert R. , Mitrofanov I. G. , Lisov D. I. , Litvak M. L. , Sanin A. B. , Vasavada A. R.
Published: April 2024

This paper is Part II of a double‐paper series that presents the abundance of water and chlorine along with other neutron‐absorbing elements in the shallow subsurface of Gale crater based on measurements by the Dynamic Albedo of Neutron (DAN) instrument onboard NASA's Curiosity rover. Initial results were represented as pixels on map data products from both DAN active and passive measurements made along the 27‐km traverse of the rover, corresponding to the mission period from landing on the martian surface in August 2012 through December 2021. In Part II, the contents of water and chlorine along with other neutron absorbers are studied separately for distinct geological regions along the traverse. Mean values and sample variances of these values are presented for each region. Water‐equivalent hydrogen (WEH) measurements show variability within the Jura member of the Murray formation and increase within the Carolyn Shoemaker formation. A large fraction of stratigraphic units (e.g., Bradbury, Sheepbed, Pahrump Hills and others) have mean WEH values between 2 and 3 wt.%, while units in the second part of the traverse (Jura, Knockfarrill Hill, Glasgow, Pontours) have mean values of WEH above 3 wt.%. The mean absorption‐equivalent chlorine value has no large variations for all tested geologic units; it is equal to around 1% for all of them.
A National‐Scale Coastal Flood Hazard Assessment for the Atoll Nation of Tuvalu
Authors: Wandres Moritz , Espejo Antonio , Sovea Tomasi , Tetoa Sapolu , Malologa Faatasi , Webb Arthur , Lewis James , Lee Gary , Damlamian Hervé
Published: April 2024

Atoll nations such as Tuvalu are considered to be amongst those most vulnerable to the effects of climate change. Here we present a national‐scale coastal flood hazard assessment for Tuvalu based on high‐resolution Light Detection and Ranging (LiDAR) topography and bathymetry. We follow a fully probabilistic approach, considering sea level anomalies, tides, and extreme wave conditions from a mixed climate (i.e., from distant extra‐tropical storms and local tropical cyclones). Nearshore processes such as wave setup and runup are also accounted for. Hazard maps were calculated for the present sea level, as well as for sea level rise projections corresponding to different shared socioeconomic pathways (SSP2 4.5 and SSP5 8.5) and time horizons (2060 and 2100). With a mean elevation of 1.55 m above mean sea level (1.37 m above mean high water spring) >25% of land area is inundated once every 5 years and >50% of land area floods once every 100 years nationally. Results indicate that present day 1‐in‐50 years floods (>45% of land area flooded) will occur more than once every 5 years by 2060 (annual exceedance probability >20%), even under the moderate SSP2 4.5 sea level rise projections. Results of this study highlight the pressing need for ambitious and large‐scale adaptation solutions which are commensurate with projected sea level rise and marine hazard impacts. The methodologies presented in this paper can easily be applied to other low‐lying islands in the tropical Pacific, where mixed climates (i.e., regular and TC conditions) and non‐linear nearshore processes dominate extreme water levels and flooding.
Relationships Between Plankton Size Spectra, Net Primary Production, and the Biological Carbon Pump
Authors: Stukel Michael R. , Décima Moira , Kelly Thomas B. , Landry Michael R. , Nodder Scott D. , Ohman Mark D. , Selph Karen E. , Yingling Natalia
Published: April 2024

Photosynthesis in the surface ocean and subsequent export of a fraction of this fixed carbon leads to carbon dioxide sequestration in the deep ocean. Ecological relationships among plankton functional groups and theoretical relationships between particle size and sinking rate suggest that carbon export from the euphotic zone is more efficient when communities are dominated by large organisms. However, this hypothesis has never been tested against measured size spectra spanning the >5 orders of magnitude found in plankton communities. Using data from five ocean regions (California Current Ecosystem, North Pacific subtropical gyre, Costa Rica Dome, Gulf of Mexico, and Southern Ocean subtropical front), we quantified carbon‐based plankton size spectra from heterotrophic bacteria to metazoan zooplankton (size class cutoffs varied slightly between regions) and their relationship to net primary production and sinking particle flux. Slopes of the normalized biomass size spectra (NBSS) varied from −1.6 to −1.2 (median slope of −1.4 equates to large 1–10 mm organisms having a biomass equal to only 7.6% of the biomass in small 1–10 μm organisms). Net primary production was positively correlated with the NBSS slope, with a particularly strong relationship in the microbial portion of the size spectra. While organic carbon export co‐varied with NBSS slope, we found only weak evidence that export efficiency is related to plankton community size spectra. Multi‐variate statistical analysis suggested that properties of the NBSS added no explanatory power over chlorophyll, primary production, and temperature. Rather, the results suggest that both plankton size spectra and carbon export increase with increasing system productivity.
Insights on the African Upper Mantle From Quasi‐Love Wave Scattering
Authors: Merry Thomas A. J. , Eakin Caroline M.
Published: April 2024

The African upper mantle is diverse, featuring several cratonic roots, active and magmatic continental rifting, abundant intra‐plate volcanism, and several oceanic hotspots offshore. Relatively small‐scale mantle convection processes, some possibly related to lithospheric thickness variations, have been proposed to account for patterns of volcanism and topography. A key constraint on such features and processes can be found via seismic anisotropy, but limited coverage of seismograph stations across the continent has resulted in sparse observations. Quasi‐Love waves, produced by scattering of Love to Rayleigh energy at lateral gradients in upper mantle seismic anisotropy, can provide information about seismic anisotropy well away from seismograph stations. We catalog 525 observations of Quasi‐Love waves across the region and back‐project to scattering points, revealing locations of lateral gradients in upper mantle seismic anisotropy. Quasi‐Love wave scattering occurs at craton edges, likely due to the contrast between lithospheric and asthenospheric anisotropy, and close to ancient orogenic belts, indicating changes in fossilized lithospheric anisotropy from past collisional events. Scattering surrounding the proposed Al‐Kufrah cratonic remnant in north‐east Africa supports its existence as cratonic lithosphere. Scattering also occurs below thin lithosphere, suggesting deviations in asthenospheric flow patterns (such as localized upwellings), notably beneath the East African Rift, oceanic hotspot tracks, and the Cameroon Volcanic Line. Quasi‐Love scattering is abundant in the Indian Ocean and beneath Madagascar, consistent with small‐scale dynamic processes in the asthenosphere that likely relate to the complex rifting history of this ocean basin and the dispersed micro‐continents within.
The Contrast Precipitation Patterns in Yangtze River Valley Between the Two La Niña Decaying Summers in 2021 and 2022
Authors: Yuan Shuai , Sun Xuguang , Zhang Xinyou , Xu Shiqi , Yang Xiu‐Qun
Published: April 2024

Although the summers of 2021 and 2022 are both in the two successive La Niña decaying stages and under the same climate background of negative Pacific Decadal Oscillation (PDO) phase and global warming trend, they exhibit significantly different and even opposite precipitation patterns in the Yangtze River Valley (YRV) as well as in the Indian monsoon region (IMR). In contrast to the abundant precipitation and lower temperature in the YRV in summer 2021, in summer 2022 the YRV experiences severe drought and extremely high temperatures, which is also accompanied by Mega‐floods in the IMR. This study identifies the joint influence of sea surface temperature anomalies (SSTAs) in Niño4 and Barents Sea (BS) regions as the underlying cause for the contrast YRV precipitation anomalies in the summers of 2021 and 2022. Specifically, the cold SSTAs in both Niño4 and BS regions in summer 2021 favor stronger and southward shifted western North Pacific subtropical high (WNPSH), leading to more precipitation in the YRV, which is however generally reversed but more intense in summer 2022 because of the synergistic effect of cold Niño4 and warm BS SSTAs. Moreover, the induced extreme precipitation in the IMR in summer 2022, which is absent in summer 2021 due to the offsetting effect of cold SSTAs in both Niño4 and BS regions, in turn further strengthens the anomalous atmospheric circulations via its released large diabatic heating and serves as a relay pathway for the dramatic drought and heat wave in the YRV.
Inter‐Comparison of Precipitation Simulation and Future Projections Over China From an Ensemble of Multi‐GCM Driven RCM Simulations
Authors: Tong Yao , Gao Xuejie , Xu Ying , Cui Xiulai , Giorgi Filippo
Published: April 2024

An analysis is presented of the precipitation bias and change signal in an ensemble of regional climate model (RCM) (RegCM4) projections driven by multiple general circulation models (GCMs) over China. RegCM4 is driven by five different GCMs for the 120‐year period 1979–2099 at 25 km grid spacing, under the representative concentration pathway RCP8.5. We find that the GCMs and RegCM4 reproduce the general spatial pattern of precipitation over China in all four seasons, with RegCM4 providing greater spatial detail, especially over areas with complex terrain. The spatial patterns of precipitation bias show common features between the GCMs and RegCM4, characterized by an underestimation in the wetter regions, and an overestimation in the drier ones. Systematic increases of precipitation are projected in northern China, most pronounced in the Northwest basins, by both the GCMs and RegCM4 in all seasons except summer, when more mixed results are found. In addition, weak correlations of the projected change patterns are found in summer between the GCMs and nested RegCM4, indicating the greater role played by the representation of local convection processes during this monsoon season. The projections across the RegCM4 experiments show higher consistency and lower spread compared to the GCM ensemble, again indicating that the nested model physics significantly modulates the change signal deriving from the GCM boundary forcing.
Hydrolysis Products of Fe(III)‐Si Systems With Different Si/(Si + Fe) Molar Ratios: Implications to Detection of Ferrihydrite on Mars
Authors: Xiang Xinyi , Du Peixin , Ye Binlong , Bu Hongling , Liu Dong , Liu Jiacheng , Hua Jian , Guo Xiaolong
Published: April 2024

Ferrihydrite, a nanocrystalline iron (oxyhydr)oxide mineral, is widely distributed in soils and sediments on Earth and is probably an important component and/or precursor of widespread nanophase iron minerals on Mars. Terrestrial ferrihydrite often co‐occurs with amorphous silica and/or contains a certain amount of Si in its structure. However, it remains ambiguous how environmental Si concentration affects the formation‐evolution and structure‐spectral features of ferrihydrite in the Fe(III)‐Si systems. To this end, hydrolysis experiments were carried out for Fe‐Si systems at an unprecedentedly wide range of initial Si/(Fe + Si) molar ratios (0–0.80), followed by characterizing the products detailly. X‐ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, Mössbauer spectroscopy, and transmission electron microscopy results showed that at Si/(Fe + Si) molar ratios ≤0.30, the main phase of the products was ferrihydrite, of which the unit cells enlarged, the crystallinity decreased, and the existing state of Fe changed with increased Si contents; at Si/(Fe + Si) molar ratios ≥0.40, ferrihydrite was no longer formed and a novel amorphous Fe‐O‐Si phase was instead obtained, with the excess Si forming amorphous silica. The visible and near‐infrared spectroscopy, the most powerful tool to detect hydrous minerals on the surface of Mars at global or regional scales, showed weakness in identifying ferrihydrite‐like materials obtained in the Fe‐Si systems. Raman spectroscopy can identify ferrihydrite and Si‐containing ferrihydrite but cannot differentiate between them. Mössbauer spectroscopy showed great potential in both identifying and differentiating between ferrihydrite and Si‐containing ferrihydrite, and thus can be used to characterize the poorly ordered iron (oxyhydr)oxides on Mars.
Lake Ice From Historical Records to Contemporary Science
Authors: Sharma S. , Shchapov K. , Culpepper J. , Magnsuon J. J.
Published: April 2024

Lake ice phenology is a critical component of the cryosphere and a sensitive indicator of climate change that has some of the longest records related to climate science. Records commenced for numerous reasons including navigation, hydropower development, and individual curiosity, demonstrating the value of lake ice as a seasonal event of significant importance to a broad swath of peoples and countries. At the same time, lake ice loss has been rapid and widespread with lakes losing ice at an average rate of 17 days per century. In this Perspective, we examine the earliest known records of ice cover and the scientific studies that developed from that practice of record keeping. Studies in lake ice began in the nineteenth Century and have included relationships between climate, biology, and ice cover. Early studies developed some of the foundational principles that limnologists and climate scientists are still exploring, such as the relationship between ice phenology and climate variables, large‐scale climate oscillations, and morphological characteristics, with implications for lake ice physical structure and under‐ice ecosystems in a warming climate. We conclude with an examination of the state of the field and how these centuries‐long lake ice records can continue to inform cutting edge science by validating satellite remote sensing techniques, in addition to modeling approaches and collaborations across disciplines, that can improve our understanding of the loss of lake ice in a warmer world.
Controls on Sediment Transport From a Glacierized Catchment in the Swiss Alps Established Through Inverse Modeling of Geomorphic Processes
Authors: Delaney Ian , Werder Mauro A. , Felix David , Albayrak Ismail , Boes Robert M. , Farinotti Daniel
Published: April 2024

As climate warms, hydrology and geomorphology in glacierized catchments are evolving, changing sediment export from these catchments, thus impacting downstream ecosystems and communities. Currently, much uncertainty persists regarding interactions among geomorphic processes that evacuate sediment from glacierized catchments. Here, we present a catchment‐scale numerical model of subglacial and proglacial sediment transport with debris meltout processes. We apply the model in a Monte Carlo framework to suspended sediment data collected over 2014–2020 from the Fieschertal catchment in the Swiss Alps, assessing possible combinations of geomorphic processes responsible for suspended sediment discharge. The ensemble of model outputs quantifies the interaction of different geomorphic processes, including the trade‐off between bedrock erosion and sediment previously stored in the catchment. Model runs suggest that, at some periods, up to 20% of the sediment leaving the glacier is deposited in the proglacial area relative to the catchment's total sediment discharge. This shows that the model captures the proglacial area change from sediment source to sediment sink in different hydrological and glaciological conditions. Furthermore, the findings highlight the impact of glacier retreat on the catchment's sediment dynamics, which both reduces the proglacial area's slope and introduces additional sediment to the proglacial area through debris meltout. The model outputs and the parameters quantify the interaction among geomorphic processes, yielding key insights into the drivers of sediment transport in alpine regions. The implications of these interactions are discussed in the context of interpreting processes responsible for controlling erosion rates from glacierized regions and modeling sediment transport in glacierized catchments.
A Novel Double Machine Learning Strategy for Producing High‐Precision Multi‐Source Merging Precipitation Estimates Over the Tibetan Plateau
Authors: Lyu Yi , Yong Bin
Published: April 2024

Precipitation estimation over the Tibetan Plateau is a critical but challenging task due to sparse gauges and high altitudes. Traditional statistic methods are often insufficient to characterize the nonlinear relationship between different precipitation information, while machine learning techniques, particularly deep learning algorithms, offer a novel and powerful approach to improve the merging accuracy of multi‐source precipitation data by efficiently capturing their spatiotemporal dynamics features. This study introduced a novel strategy called Double Machine Learning (DML), which integrates meteorological information, satellite retrievals, and reanalysis data to produce a high‐precision multi‐source merging precipitation product at 0.1° × 0.1°, daily resolution for the Tibetan Plateau. The quantitative evaluation of DML was accomplished using both auto‐meteorological gauges and independent observations. Statistical scores indicate that the new DML‐based merging product apparently outperforms three widely‐used precipitation datasets (IMERG‐Final, GSMaP‐Gauge and ERA5) over the Tibetan Plateau. The proposed DML strategy effectively integrates the advantages of traditional machine learning and deep learning, significantly enhancing the algorithmic robustness and merging accuracy, particularly at medium‐high rain rates in summer. Furthermore, the contributions of multi‐source inputs to the final merging effect was systematically analyzed. It is found that meteorological information, as an auxiliary variable in DML, plays a crucial role in identifying rainy events and adjusting the bias of precipitation estimates, especially over those ungauged regions. This study affirms the call for improving the multi‐source precipitation estimates by combining different machine learning approaches. The new merging precipitation product reported here is recommended for hydrometeorological users of the Tibetan Plateau science community.
Leveraging Next‐Generation Satellite Remote Sensing‐Based Snow Data to Improve Seasonal Water Supply Predictions in a Practical Machine Learning‐Driven River Forecast System
Authors: Fleming Sean W. , Rittger Karl , Oaida Taglialatela Catalina M. , Graczyk Indrani
Published: April 2024

Seasonal predictions of spring‐summer river flow volume (water supply forecasts, WSFs) are foundational to western US water management. We test a new space‐based remote sensing product, spatially and temporally complete (STC) MODSCAG fractional snow‐covered area (fSCA), as input for the Natural Resources Conservation Service (NRCS) operational US West‐wide WSF system. fSCA data were considered alongside traditional SNOTEL predictors, in both statistical and AI‐based NRCS operational hydrologic models, throughout the forecast season, in four test watersheds (Walker, Wind, Piedra, and Gila Rivers in California, Wyoming, Colorado, and New Mexico). Outcomes from over 200 WSF models suggest fSCA‐enabled accuracy gains are most consistent and explainable for short‐lead, late‐season forecasts (roughly 10%–25% improvements, typically), which in operational practice can be challenging as snowlines rise above in situ measurement sites. Gains are roughly proportional to how thoroughly spring‐summer runoff is dominated by snowmelt, and how poorly in situ networks monitor late‐season snowpack. fSCA also improved accuracy for long‐lead, early‐season forecasts, which are similarly problematic in WSF practice, but not for WSFs issued around the time of peak snow accumulation, when in situ measurements reasonably characterize mountain snowpack available for upcoming spring‐summer snowmelt. The AI‐based hydrologic model generally outperformed the statistical model and, in some cases, better‐capitalized on satellite remote sensing. Additionally, preliminary analyses suggest reasonable WSF skill in many cases using fSCA as the sole predictor, potentially useful in sparsely monitored regions; and that combining satellite and in situ products in data‐driven hydrologic models using genetic algorithm‐based predictor selection could help guide new SNOTEL site selection.
Recent advances in extracellular vesicles for therapeutic cargo delivery
Authors: Kim Hyo In , Park Jinbong , Zhu Yin , Wang Xiaoyun , Han Yohan , Zhang Duo
Published: April 2024

Exosomes, which are nanosized vesicles secreted by cells, are attracting increasing interest in the field of biomedical research due to their unique properties, including biocompatibility, cargo loading capacity, and deep tissue penetration. They serve as natural signaling agents in intercellular communication, and their inherent ability to carry proteins, lipids, and nucleic acids endows them with remarkable therapeutic potential. Thus, exosomes can be exploited for diverse therapeutic applications, including chemotherapy, gene therapy, and photothermal therapy. Moreover, their capacity for homotypic targeting and self-recognition provides opportunities for personalized medicine. Despite their advantages as novel therapeutic agents, there are several challenges in optimizing cargo loading efficiency and structural stability and in defining exosome origins. Future research should include the development of large-scale, quality-controllable production methods, the refinement of drug loading strategies, and extensive in vivo studies and clinical trials. Despite the unresolved difficulties, the use of exosomes as efficient, stable, and safe therapeutic delivery systems is an interesting area in biomedical research. Therefore, this review describes exosomes and summarizes cutting-edge studies published in high-impact journals that have introduced novel or enhanced therapeutic effects using exosomes as a drug delivery system in the past 2 years. We provide an informative overview of the current state of exosome research, highlighting the unique properties and therapeutic applications of exosomes. We also emphasize challenges and future directions, underscoring the importance of addressing key issues in the field. With this review, we encourage researchers to further develop exosome-based drugs for clinical application, as such drugs may be among the most promising next-generation therapeutics.