bluuebunny/crossref_metadata_2025 huggingface dataset:
Deflagration-to-detonation transition and detonation propagation in supersonic flows with hydrogen injection and downstream ignition
Authors: Cai Xiaodong , Wang Xinxin , Liu Haorui , Hong Rong , He Han
Published: October 2024

This study investigates the mechanisms of flame acceleration and deflagration-to-detonation transition (DDT) in supersonic flows using transverse hydrogen injection and downstream ignition. Utilizing the graphics processing unit accelerated adaptive mesh refinement approach, we examine the influence of downstream ignition jet pressure on DDT through high-resolution computational simulations. Our results indicate that the transverse injection of hydrogen into the supersonic mainstream generates strong turbulence and numerous vortices due to Kelvin–Helmholtz instability, enhancing fuel mixing efficiency along the flow but deviating from the ideal premixed state. Following the injection of the downstream ignition jet into the supersonic main flow, initial flame acceleration is less effective than in the premixed state due to the non-uniformity of the incoming flow. However, within the boundary layer, the flame remains stable, and the intense turbulence fosters shock–flame interactions. The convergence of multiple compression waves into a shock wave facilitates energy deposition, coupling with the flame to trigger local detonation via the reactive gradient mechanism. The detonation wave exhibits complex wavefront structures, including vertical and oblique fronts induced by boundary layer interactions. Ignition jet pressure significantly impacts the DDT process and detonation wave characteristics, reducing ignition time and affecting the detonation temperature, pressure, and propagation speed. This study provides valuable insights into the dynamics of flame acceleration and DDT in supersonic flows with non-uniform fuel distribution and downstream jet ignition. The findings highlight the critical role of ignition jet pressure in optimizing ignition and detonation processes, offering new perspectives for achieving low-energy, rapid detonation initiation within the tube.
Performance enhancement of frequency-doubling gyroklystron amplifier by magnetic field tapering
Authors: Singh Abhijeet , Chauhan Madan Singh , Srivastava Neelam
Published: October 2024

A uniform magnetic field across the device is often used to analyze gyroklystron. In this paper, a tapered magnetic field is applied across the two-cavity 35 GHz frequency-doubling gyroklystron to improve its performance. Device performance is compared between tapered and uniform magnetic field cases using particle-in-cell code “CST.” The result confirms that the tapered magnetic field significantly improves the device performance parameters such as output power, efficiency, gain, and bandwidth compared to uniform magnetic field conditions. With a 1.6-kW driver power, 306 kW RF output power along with 22.8 dB gain is achieved for a tapered magnetic field case, while 227 kW RF output power along with 21.5 dB gain is achieved for a uniform magnetic field case. When the magnetic field is uniform, the efficiency and bandwidth of a gyroklystron are approximately 21.6% and 100 MHz, respectively; however, for the tapered magnetic field, it can rise to 29.1% and 120 MHz, respectively. Device efficiency results suggest that a tapered magnetic field improves energy transfer from the electron beam to the RF field. A parametric study for both magnetic field cases examines the effect of magnetic field strength, beam current, beam voltage, and pitch factor on the device. This detailed research recommends optimizing frequency-doubling gyroklystron performance with tapered magnetic fields.
A novel multi-excitation transient vibration framework for coupling three- and one-dimensional pumped storage hydropower shafting systems
Authors: Feng Chen , Sun Jie , Zhang Yuquan , Zheng Yuan
Published: October 2024

In vibration models of shafting systems, the hydraulic excitation is difficult to characterize due to the complex and changeable hydraulic factors. Thus, hydropower units are not well understood in terms of their dynamics and stability control under transient processes. A hydraulic–mechanical–electric multi-excitation transient vibration calculation framework is developed for analyzing the relationship between shafting vibration and internal flow regimes. First, the boundary data from penstocks, tailraces, and hydro-turbine are interacted with using one-dimensional and three-dimensional (1D–3D) coupling; Second, user-defined function secondary development is applied to achieve two-stage guide vane closure and the runner's variable speed rotation; Third, based on the computational fluid dynamics results, a multi-excitation vibration model is established to analyze shafting system characteristics. There is less than 1.2% error between the algorithm and the field test in terms of speed peak values. Under braking or reverse pumping modes, various vortice clusters are generated in the blade channel as well as the cascade, blocking the flow passage and leading to the runner's unbalanced force. Three sudden increases in vibration amplitudes of the shafting system have occurred in the radial direction under load rejection, each corresponded to the runner's stall rotations. The change trend in axial vibration amplitudes, however, is closely related to the change in axial hydraulic thrust. Furthermore, in braking and reverse pumping conditions, the axis trajectory is more complex under the action of multiple coupling factors than when only hydraulic factors are considered.
Benchmark problems for simulating Hyperloop aerodynamics
Authors: Lang Alex J. , Connolly David P. , Boer Gregory de , Shahpar Shahrokh , Hinchliffe Benjamin , Gilkeson Carl A.
Published: October 2024

Hyperloop is proposed as the next generation of sustainable high-speed transport. Recently, an increasing body of literature has been amassed on Hyperloop aerodynamics, however, the vast majority of this work is numerical. Experimentally, there are few relevant studies and none are suitable for validating computational approaches. This paper presents three benchmark cases to provide a framework for computational research and to address this significant gap. Benchmark 1 provides experimental data from existing work on a projectile traveling at Mach 1.1 in ground effect. This incorporates many of the flow characteristics of a Hyperloop system, including (i) transonic Mach numbers, (ii) wall confinement, and (iii) shock formation/reflection. These experimental data are compared to Computational Fluid Dynamics simulations with a very good match seen. Next, Benchmark 2 is proposed which extends these simulations toward a baseline Hyperloop pod design operating in an axisymmetric low-pressure tube environment. This is achieved in stages by adding a full tube, scaling up the domain, reducing the air pressure, and introducing a baseline pod design. It is shown that the enclosed tube environment causes the most significant change in aerodynamic characteristics via flow choking. Nevertheless, a number of aerodynamic similarities remain, compared to Benchmark 1. Finally, Benchmark 3 is proposed to explore the impact of ground clearance of the pod. This aspect has a significant influence on the flow by deflecting the wake and the downstream shock pattern. Furthermore, the drag, downforce, and pitching moment are all found to increase with lower ground clearances.
Dynamics optimization of coupling atomization process in an injector achieved by novel micro laser powder bed fusion
Authors: Zhai Zirong , Zhao Rongfa , Cheng Yongying , Yue Ming , Fan Jiang , Wu Yingna , Yang Rui , Wang Weihao
Published: October 2024

This study employed large eddy simulation and a volume-of-fluid with discrete phase model to evaluate a swirl fuel injector's atomization performance. Addressing non-uniform atomization at low flow rates, the study optimized a swirl injector structure based on additive manufacturing advantages during re-modeling. Computational analysis revealed that vortex downstream and capillary bubbles caused non-uniformity in the prototype injector, mitigated by the optimized injector's three-dimensional flow channel. Comparative analysis showed similar parameters between the optimized and prototype injectors, except for significant improvement in circumferential uniformity at low flow rates (from 41.48% to 14.69%). The optimized injector's swirl structure, produced via micro laser powder bed fusion, exhibited precise dimensions and minimal surface roughness. Validation experiments without air inflow confirmed the computational results' reliability, with a minor discrepancy in circumferential uniformity (2.98%) and atomization cone angle (2.3°) for the prototype swirl structure. At low flow rates, the optimized structure showcased reduced circumferential non-uniformity (from 42.31% to 28.76%), underscoring its benefits. This interdisciplinary investigation underscores additive manufacturing's application in structural optimization and manufacturing.
A nonequilibrium statistical mechanics derivation of the hydrodynamic equations of simple fluids using a noncanonical form of the Poisson bracket
Authors: Edwards Brian J. , Beris Antony N.
Published: October 2024

The continuum level hydrodynamic equations of a simple fluid were derived by Irving and Kirkwood directly from discrete particle dynamics using statistical mechanics almost 75 years ago. Their elegant derivation demonstrated the fundamental molecular basis of macroscopic fluid flow and culminated in molecular expressions for the stress tensor and heat current density that have since been employed in countless molecular simulations to date. In this article, an alternative derivation is presented, which leads to more general expressions for the fundamental transport relationships and which arrives at them in a more straightforward chain of consistency that ensues directly from the Principle of Least Action. The main point of departure from the Irving–Kirkwood derivation is the application of a transformation mapping of the total momentum of each individual particle onto the sum of its peculiar momentum and its momentum relative to the local velocity field. This mapping provides a phase-space distribution function applicable in the space of particle positions and peculiar momentum, from which a noncanonical Poisson bracket can be derived in terms of the same set of microscopic variables. For a given dynamic variable, expressed in terms of particle positions and peculiar momenta, the expectation value of the noncanonical Poisson bracket of the dynamic variable is shown to correspond to the evolution equation of the expectation value of the dynamic variable. This allows for a direct derivation of all macroscopic density evolution equations (mass, momentum, and energy density fields) using a systematic procedure free of assumptions concerning the macroscopic state of the system. Furthermore, an explicit expression of the time evolution of the entropy density at the hydrodynamic level is derived following the same procedure. Finally, in the limit of short-range interparticle interactions, a molecular-based expression for the local stress tensor as properly defined from continuum mechanics is developed at the hydrodynamic level that elucidates the continuum mechanics connection of the general stress expression of Irving and Kirkwood.
Resonance and surfactant effects on the interaction of a rising bubble and a sedimenting particle in an oscillating fluid
Authors: Klimenko Lyudmila , Lyubimova Tatyana
Published: October 2024

This paper considers the interaction of a rising bubble and a sedimenting fine particle in a liquid with a soluble surfactant subjected to the gravity field, forced flow, and vibrations. The frequency of vibrations is close to the resonance value. The particle motion trajectories are calculated, taking into account its inertia, fluid viscosity, Basset force, buoyancy force, and the mean force acting on the particle due to the inhomogeneity of the pulsating field. The collision efficiency is evaluated, and the cross sections of the sedimenting particles captured by the rising bubble are found. It is demonstrated that even at low vibration intensity but in the presence of a weak surfactant effect, a significant increase in the probability of particle–bubble collision and in the capture cross section can be achieved. The obtained results can be used to intensify the flotation processes by ultrasonic treatment.
Numerical investigation of non-equilibrium condensation of carbon dioxide from a gas mixture of carbon dioxide and argon in a supersonic nozzle under cryogenic conditions
Authors: Yoon Sang Hee , Kim Sung Jin , Yu Sangseok , Kim Byoung Jae
Published: October 2024

This study involved a numerical investigation of the homogeneous nucleation of CO2 from a CO2–Ar gas mixture in a supersonic nozzle with a throat size of 2.11 mm, a total pressure of 61.15 kPa, and a total temperature of 293.15 K. The flow conditions covered the cryogenic temperature range (∼75 K). Therefore, the surface tension of the clusters was calculated using the Tolman–Tanaka correction, and nucleation growth was evaluated considering both free molecular and continuum regimes. Numerical simulations were conducted for a wide range of CO2 mole fractions (3%–39%). In particular, the effect of the CO2 mole fraction on the condensation-shock position—approximately the Wilson point—was investigated. For 3%, 12%, 24%, and 39%, the condensation shock occurred at 0.048, 0.043, 0.046, and 0.054 m from the throat, respectively. When the mole fraction was low (≤10%), the condensation-shock position moved downstream as the mole fraction decreased. This trend was attributed to a lower nucleation rate. In contrast, when the mole fraction was high (≥10%), the condensation-shock position moved downstream as the mole fraction increased. This was because the CO2 equilibrium pressure rose more rapidly than the CO2 vapor pressure as the mole fraction increases.
Mechanically forced meniscus water waves in a square container with functionalized wetting conditions
Authors: Zhang Shimin , Borthwick Alistair G. L. , Lin Zhiliang
Published: October 2024

Capillary–gravity surface waves, called meniscus waves, are excited at the air–water interface near the lateral boundary of a mechanically forced square container. Experiments are conducted in two working containers: one is overall hydrophilic at four boundaries and the other is functionalized to have a hydrophobic boundary. The static meniscus structures and instantaneous wave topography are reconstructed at high resolution from the side-view and top-view high-speed camera recordings. Wave resonances arise from the interaction of four inward-traveling waves, with the frequency-response characteristics indicating the effect of wetting conditions on the selection of standing wave patterns. The most-resonant modes are identified as a superposition of dominant modes and higher-order components. An analytical model of the rest-state meniscus and resonant-state wave surface decomposes the wave responses into two groups of resonances along two transverse directions linked by a frequency-dependent parameter γ. Theoretical selection of the dominant wave components and the second-order harmonics is in close agreement with the spatiotemporal surface-fitting experimental results. Additionally, the wetting boundary conditions can be functionalized to excite specific standing wave patterns, which could provide a novel approach to precise pattern control in bioprinting technology for tissue engineering applications.
Experimental investigation of the influence of ZnO–CuO nanocomposites on interfacial tension, contact angle, and oil recovery by spontaneous imbibition in carbonate rocks
Authors: Mansouri Mohsen , Ahmadi Yaser , Sedghamiz Mohammad Amin , Vaferi Behzad
Published: October 2024

Researchers have recently focused on applying various nanoparticles/nanocomposites to improve the recovery factor from oil reservoirs. In this study, a new enhanced oil recovery agent, i.e., a ZnO–CuO (ZCO) nanocomposite, was synthesized, and its physicochemical properties are investigated by the scanning electron microscope, Fourier transform infrared spectrometer, Brunauer–Emmett–Teller, X-ray diffraction, and energy diffraction x-rays. The impact of ZCO and ZnO on interfacial tension, wettability change, and zeta potential tests has also been investigated under reservoir conditions. 0.1 weight percent (wt.%) of ZnO and ZCO in injection fluid, which minimizes contact angle and maximizes stability (i.e., minimum zeta potential), has been determined as the optimum concentration. The contact angle and zeta potential at this optimum concentration of ZnO and ZCO are 50.83°, 35.69° and −31.38, −35.65 mV, respectively. Then, the spontaneous imbibition using ZnO- and ZCO-based nanofluids with the optimum concentration is applied to monitor the recovery factor. The 22.5 day-long imbibition operation utilizing base fluid (without nanomaterials), ZnO, and ZCO retrieved 24.95%, 35.74%, and 52.01% of the oil, respectively. Overall, we concluded that injecting the ZCO-based nanofluids in carbonate porous media efficiently improves rocks and fluid parameters and enhances oil recovery.
Mechanical behavior of water ingress process for the locally damaged submerged floating tunnel and its interpretation: A full-length experimental study
Authors: Xie Canrong , Pan Zhuang , Wu Zhiwen , Wu Guangze , Garg Ankit , Mei Guoxiong
Published: October 2024

The submerged floating tunnel (SFT) is an innovative transportation solution for traversing deep-water regions. However, local damage and subsequent water ingress pose significant threats to the structural integrity and safety of SFTs. This critical issue has been unexplored in the field. This study addresses this gap by presenting a comprehensive experimental investigation using a full-length physical model of the SFT. The dynamic response and failure mechanisms caused by water ingress within the SFT tube, influenced by various factors such as immersion depth, damaged opening angle, damaged opening area, and external connectivity, are systematically investigated. The results indicate that the failure of the anchor cable and tube structure of the SFT progresses through three stages after water ingress occurs in the damaged SFT. It is observed that damage closer to the bottom of the tube reduces the risk of failure in the mooring system. Notably, air pressure is a critical factor influencing the water ingress into the tube body. The attenuation of cable tension and tube deformation is significantly slower when the internal air is isolated from the external environment. The proposed novel structural sealing segmental disaster prevention design scheme substantially mitigates the risk of structural damage under compromised conditions and water ingress. This study provides valuable insights into enhancing disaster prevention strategies for SFTs and advances the understanding of their mechanical behavior in response to damage and water ingress.
An implicit adaptive unified gas-kinetic scheme for steady-state solutions of nonequilibrium flows
Authors: Long Wenpei , Wei Yufeng , Xu Kun
Published: October 2024

In recent years, nonequilibrium flows have been frequently encountered in various aerospace engineering and micro-electro-mechanical systems applications. To understand nonequilibrium physics, multiscale effects, and the dynamics in these applications, a reliable multiscale scheme for all flow regimes is required. Following the direct modeling methodology, the adaptive unified gas-kinetic scheme employs discrete velocity space to accurately capture the nonequilibrium physics, recovering the original unified gas-kinetic scheme (UGKS). By adaptively employing continuous distribution functions based on the Chapman–Enskog expansion, it efficiently handles near-equilibrium flow regions. The two regions are dynamically coupled at the cell interface through the fluxes from the discrete and continuous gas distribution functions, thereby avoiding any buffer zone between them. In this study, an implicit adaptive unified gas-kinetic scheme (IAUGKS) is constructed to further enhance the efficiency of steady-state solutions. The current scheme employs implicit macroscopic governing equations and couples them with implicit microscopic governing equations within the nonequilibrium region, resulting in high convergence efficiency in all flow regimes. To validate the efficiency and robustness of the IAUGKS, a series of numerical tests were conducted for high Mach number flows around diverse geometries. The current scheme can capture the nonequilibrium physics and provide accurate predictions of surface quantities. In comparison with the original UGKS, the velocity space adaptation, unstructured discrete velocity space, and implicit iteration significantly improve the efficiency by one or two orders of magnitude. Given its exceptional efficiency and accuracy, the IAUGKS serves as an effective tool for nonequilibrium flow simulations.
Graphene-enhanced ferroelectric domain wall high-output memristor
Authors: Risch Felix , Gilani Ali , Kamaei Sadegh , Ionescu Adrian M. , Stolichnov Igor
Published: October 2024

Recent studies on memristive materials and technologies have expanded beyond conventional memory elements, driven by their potential application in novel information processing concepts. Among these materials, conductive domain walls in ferroics are especially promising, offering conductive tunability suitable for reconfigurable multi-state devices. However, challenges such as domain stability, time-dependent conductivity, and low current output have impeded progress in the field. Here, we study the graphene/Pb(Zr,Ti)O3/SrRuO3 system, which demonstrates robust domain wall conduction up to 100 nA/μm2 for 2 V bias, while addressing the critical issue of stability of switched domains. The introduction of graphene electrodes enhances low-voltage stochastic domain formation with limited domain expansion that promotes the emergence of multi-domain states. The developed micrometer sized capacitor devices enable electrically programmable multiple distinct conduction states with robust retention combined with high current output and low operation voltage. These features are highly desirable for memristors and mark the significant potential of domain wall electronics for neuromorphic computing.
Study on suction effect of water jet propulsion pump based on entropy weight theory
Authors: Zhao Heng , Cheng Li , Sheng Weigao , Jiao Weixuan , Luo Can
Published: October 2024

Water jet propulsion pumps start at special stages such as mooring and sailing, the ship is in shallow water, and the underwater keen clearance (UKC) is relatively small, which is easy to induce underwater suction vortex near the inlet position and cause violent vibration of the pumping unit. The powerful suction effect of the water-jet propulsion pump can draw in debris from the bottom of the riverbed, causing damage to the propulsion pump. This research investigated the suction effect of water jet propulsion pump under different UKC conditions. A flow field analysis method based on the entropy weight theory was constructed to reveal the flow characteristics of the flow field where the underwater suction vortex occurs. The research found that the suction effect on the flow field tends to stabilize under the condition of UKC greater than 2.5D0. After UKC reaches 4.2D0, suction effects essentially cease to create large-scale shear stresses near the riverbed. In addition, this research analyzes the vorticity field using vorticity and net circulation to elucidate the vortex strength within the flow field under different UKC conditions. The probability of generation of underwater suction vortices will be greatly reduced when the UKC is greater than 0.83D0.
Bifurcation of rotating surface switching at different spin-up accelerations
Authors: Skripkin Sergey G. , Naumov Igor V.
Published: October 2024

It has been found, for the first time, that rotating polygons (m = 1, 2) can exist in a system of two immiscible fluids, which can be in three different steady states: stable funnel, cycling switching, and rotating twin funnel. These states are achieved due to different disk acceleration values at fixed aspect ratio (h/R) = 1 and Reynolds numbers. The acceleration time of rotating disk is found to have a significant effect on instability development.
Numerical simulation of the effects of pulsed injection on combustion and flow processes in a supersonic combustor
Authors: He Zan , Tian Ye , Le Jialing
Published: October 2024

This paper describes two-dimensional numerical simulations of pulsed injection to a hydrogen-fueled air-breathing ramjet using the Reynolds-averaged Navier–Stokes method. We analyze the effects of sinusoidal pulsed injection on the start-up ignition time, start-up ignition range, combustion efficiency, and flow field evolution of the ramjet and compare the performance with that of steady injection. The results show that pulsed injection shortens the ignition time and optimizes the ignition equivalence ratio of hydrogen. Pulsed injection also improves the combustion efficiency of hydrogen, increasing the thrust of the engine by 7.79% compared with steady injection under the same equivalence ratio. We find that pulsed injection can cause oscillations in the ramjet combustion flow field, and show that the oscillation frequency is affected by the pulsed injection frequency.
Highly enriched carbon and oxygen isotopes in carbonate-derived CO
2
at Gale crater, Mars
Authors: Burtt David G. , Stern Jennifer C. , Webster Christopher R. , Hofmann Amy E. , Franz Heather B. , Sutter Brad , Thorpe Michael T. , Kite Edwin S. , Eigenbrode Jennifer L. , Pavlov Alexander A. , House Christopher H. , Tutolo Benjamin M. , Des Marais David J. , Rampe Elizabeth B. , McAdam Amy C. , Malespin Charles A.
Published: October 2024

Carbonate minerals are of particular interest in paleoenvironmental research as they are an integral part of the carbon and water cycles, both of which are relevant to habitability. Given that these cycles are less constrained on Mars than they are on Earth, the identification of carbonates has been a point of emphasis for rover missions. Here, we present carbon (δ
13
C) and oxygen (δ
18
O) isotope data from four carbonates encountered by the Curiosity rover within the Gale crater. The carbon isotope values range from 72 ± 2‰ to 110 ± 3‰ Vienna Pee Dee Belemnite while the oxygen isotope values span from 59 ± 4‰ to 91 ± 4‰ Vienna Standard Mean Ocean Water (1 SE uncertainties). Notably, these values are isotopically heavy (
13
C- and
18
O-enriched) relative to nearly every other Martian material. The extreme isotopic difference between the carbonates and other carbon- and oxygen-rich reservoirs on Mars cannot be reconciled by standard equilibrium carbonate–CO
2
fractionation, thus requiring an alternative process during or prior to carbonate formation. This paper explores two processes capable of contributing to the isotopic enrichments: 1) evaporative-driven Rayleigh distillation and 2) kinetic isotope effects related to cryogenic precipitation. In isolation, each process cannot reproduce the observed carbonate isotope values; however, a combination of these processes represents the most likely source for the extreme isotopic enrichments.
Impaired axon initial segment structure and function in a model of
ARHGEF9
developmental and epileptic encephalopathy
Authors: Wang Wanqi , Williams Damian J. , Teoh Jia Jie , Soundararajan Divyalakshmi , Zuberi Aamir , Lutz Cathleen M. , Frankel Wayne N. , Makinson Christopher D.
Published: October 2024

Developmental and epileptic encephalopathies (DEE) are rare but devastating and largely intractable childhood epilepsies. Genetic variants in
ARHGEF9
, encoding a scaffolding protein important for the organization of the postsynaptic density of inhibitory synapses, are associated with DEE accompanied by complex neurological phenotypes. In a mouse model carrying a patient-derived
ARHGEF9
variant associated with severe disease, we observed aggregation of postsynaptic proteins and loss of functional inhibitory synapses at the axon initial segment (AIS), altered axo-axonic synaptic inhibition, disrupted action potential generation, and complex seizure phenotypes consistent with clinical observations. These results illustrate diverse roles of ARHGEF9 that converge on regulation of the structure and function of the AIS, thus revealing a pathological mechanism for
ARHGEF9
-associated DEE. This unique example of a neuropathological condition associated with multiple AIS dysfunctions may inform strategies for treating neurodevelopmental diseases.
Innovations through crop switching happen on the diverse margins of US agriculture
Authors: Kling Matthew M. , Brittain Christopher T. , Galford Gillian L. , Waring Timothy M. , Hébert-Dufresne Laurent , Dube Matthew P. , Sabzian Hossein , Gotelli Nicholas J. , McGill Brian J. , Niles Meredith T.
Published: October 2024

Crop switching, in which farmers grow a crop that is novel to a given field, can help agricultural systems adapt to changing environmental, cultural, and market forces. Yet while regional crop production trends receive significant attention, relatively little is known about the local-scale crop switching that underlies these macrotrends. We characterized local crop-switching patterns across the United States using the US Department of Agriculture (USDA) Cropland Data Layer, an annual time series of high resolution (30 m pixel size) remote-sensed cropland data from 2008 to 2022. We found that at multiple spatial scales, crop switching was most common in sparsely cultivated landscapes and in landscapes with high crop diversity, whereas it was low in homogeneous, highly agricultural areas such as the Midwestern corn belt, suggesting a number of potential social and economic mechanisms influencing farmers’ crop choices. Crop-switching rates were high overall, occurring on more than 6% of all US cropland in the average year. Applying a framework that classified crop switches based on their temporal novelty (crop introduction versus discontinuation), spatial novelty (locally divergent versus convergent switching), and categorical novelty (transformative versus incremental switching), we found distinct spatial patterns for these three novelty dimensions, indicating a dynamic and multifaceted set of cropping changes across US farms. Collectively, these results suggest that innovation through crop switching is playing out very differently in various parts of the country, with potentially significant implications for the resilience of agricultural systems to changes in climate and other systemic trends.
Revised mechanism of hydroxyurea-induced cell cycle arrest and an improved alternative
Authors: Shaw Alisa E. , Mihelich Mattias N. , Whitted Jackson E. , Reitman Hannah J. , Timmerman Adam J. , Tehseen Muhammad , Hamdan Samir M. , Schauer Grant D.
Published: October 2024

Replication stress describes endogenous and exogenous challenges to DNA replication in the S-phase. Stress during this critical process causes helicase–polymerase decoupling at replication forks, triggering the S-phase checkpoint, which orchestrates global replication fork stalling and delayed entry into G2. The replication stressor most often used to induce the checkpoint response in yeast is hydroxyurea (HU), a clinically used chemotherapeutic. The primary mechanism of S-phase checkpoint activation by HU has thus far been considered to be a reduction of deoxynucleotide triphosphate synthesis by inhibition of ribonucleotide reductase (RNR), leading to helicase–polymerase decoupling and subsequent activation of the checkpoint, facilitated by the replisome-associated mediator Mrc1. In contrast, we observe that HU causes cell cycle arrest in budding yeast independent of both the Mrc1-mediated replication checkpoint response and the Psk1-Mrc1 oxidative signaling pathway. We demonstrate a direct relationship between HU incubation and reactive oxygen species (ROS) production in yeast and human cells and show that antioxidants restore growth of yeast in HU. We further observe that ROS strongly inhibits the in vitro polymerase activity of replicative polymerases (Pols), Pol α, Pol δ, and Pol ε, causing polymerase complex dissociation and subsequent loss of DNA substrate binding, likely through oxidation of their integral iron–sulfur (Fe-S) clusters. Finally, we present “RNR-deg,” a genetically engineered alternative to HU in yeast with greatly increased specificity of RNR inhibition, allowing researchers to achieve fast, nontoxic, and more readily reversible checkpoint activation compared to HU, avoiding harmful ROS generation and associated downstream cellular effects that may confound interpretation of results.
Tracking the progeny of bacterial persisters using a CRISPR-based genomic recorder
Authors: Rycroft Julian Anthony , Giorgio Rachel Teresa , Sargen Molly , Helaine Sophie
Published: October 2024

The rise of antimicrobial failure is a global emergency, and causes beyond typical genetic resistance must be determined. One probable factor is the existence of subpopulations of transiently growth-arrested bacteria, persisters, that endure antibiotic treatment despite genetic susceptibility to the drug. The presence of persisters in infected hosts has been successfully established, notably through the development of fluorescent reporters. It is proposed that infection relapse is caused by persisters resuming growth after cessation of the antibiotic treatment, but to date, there is no direct evidence for this. This is because no tool or reporter currently exists to track the extent to which infection relapse is initiated by regrowth of persisters in the host. Indeed, once they have transitioned out of the persister state, the progeny of persisters are genetically and phenotypically identical to susceptible bacteria in the population, making it virtually impossible to ascertain the source of relapse. We designed pSCRATCH (plasmid for Selective CRISPR Array expansion To Check Heritage), a molecular tool that functions to record the state of antibiotic persistence in the genome of
Salmonella
persisters. We show that pSCRATCH successfully marks persisters by adding spacers in their CRISPR arrays and the genomic label is stable in persister progeny after exit from persistence. We further show that in a
Salmonella
infection model the system enables the discrimination of treatment failure originating from persistence versus resistance. Thus, pSCRATCH provides proof of principle for stable marking of persisters and a prototype for applications to more complex infection models and other pathogens.
Limits on inferring T cell specificity from partial information
Authors: Henderson James , Nagano Yuta , Milighetti Martina , Tiffeau-Mayer Andreas
Published: October 2024

A key challenge in molecular biology is to decipher the mapping of protein sequence to function. To perform this mapping requires the identification of sequence features most informative about function. Here, we quantify the amount of information (in bits) that T cell receptor (TCR) sequence features provide about antigen specificity. We identify informative features by their degree of conservation among antigen-specific receptors relative to null expectations. We find that TCR specificity synergistically depends on the hypervariable regions of both receptor chains, with a degree of synergy that strongly depends on the ligand. Using a coincidence-based approach to measuring information enables us to directly bound the accuracy with which TCR specificity can be predicted from partial matches to reference sequences. We anticipate that our statistical framework will be of use for developing machine learning models for TCR specificity prediction and for optimizing TCRs for cell therapies. The proposed coincidence-based information measures might find further applications in bounding the performance of pairwise classifiers in other fields.
Closing the geologic carbon cycle
Authors: Derry Louis A.
Published: October 2024

Estimates of sedimentary organic carbon burial fluxes based on inventory and isotope mass balance methods have been divergent. A new calculation of the isotope mass balance using a revised assessment of the inputs to the ocean-atmosphere system resolves the apparent discrepancy. Inputs include weathering of carbonate and old kerogen, geogenic methane oxidation, and volcanic and metamorphic degassing. Volcanic and metamorphic degassing comprise ≈23% of the total C input. Inputs from isotopically light
OCpetro
and

CH
4-geo

drive the mean δ
13
C of the input to =−8.0 ± 1.9‰, notably lower than the commonly assumed volcanic degassing value. The isotope mass balance model yields a modern burial flux =15.9 ± 6.6 Tmol y
−1
. The impact of the mid-Miocene Climatic Optimum isotope anomaly is an integrated excess deposition ≈ 4.3 × 10
6
Tmol between 18 and 11 Ma, which is both longer and larger than estimates for the total degassing by the Columbia River Basalt eruptions, implying a complex carbon system response to large eruptive events. Monte Carlo evaluation finds that late Cenozoic net growth of the carbonate reservoir is very likely while net growth of the

C
org

reservoir is less certain but more likely than not. At present, subduction does not appear to keep up with net sedimentation and the overall masses of sedimentary carbonate and organic carbon are likely increasing. Growth in the sedimentary

C
org

reservoir implies oxidation of the surface environment and likely increases in atmospheric pO
2
.
Architecture-driven quantitative nanoscopy maps cytoskeleton remodeling
Authors: Liu Wenjie , Yao Yushi , Meng Jia , Qian Shuhao , Han Yubing , Zhou Lingxi , Wang Tao , Chen Youhua , Chen Lingmei , Ye Zitong , Xu Liang , Zhang Meng , Qiu Jianrong , Han Tao , Liu Xu , Kuang Cuifang , Ding Zhihua , Liu Zhiyi
Published: October 2024

Cytoskeleton remodeling which generates force and orchestrates signaling and trafficking to govern cell migration remains poorly understood, partly due to a lack of an investigation tool with high system flexibility, spatiotemporal resolution, and computational sensitivity. Herein, we developed a multimodal superresolution imaging system–based architecture-driven quantitative (ADQ) framework in spatiotemporal-angular hyperspace to enable both identification of the optimal imaging mode with well-balanced fidelity and phototoxicity and accurate postcharacterization of microtubule remodeling. In the ADQ framework, a pixel/voxel-wise metric reflecting heterogeneous intertubule alignment was proposed with improved sensitivity over previous efforts and further incorporated with temporal features to map dynamic microtubule rearrangements. The ADQ framework was verified by assessing microtubule remodeling in drug-induced (de)polymerization, lysosome transport, and migration. Different remodeling patterns from two migration modes were successfully revealed by the ADQ framework, with a front–rear polarization for individual directed migration and a contact site–centered polarization for cell–cell interaction-induced migration in an immune response model. Meanwhile, these migration modes were found to have consistent orientation changes, which exhibited the potential of predicting migration trajectory.
The cerebellum acts as the analog to the medial temporal lobe for sensorimotor memory
Authors: Hadjiosif Alkis M. , Gibo Tricia L. , Smith Maurice A.
Published: October 2024

The cerebellum is critical for sensorimotor learning. The specific contribution that it makes, however, remains unclear. Inspired by the classic finding that for declarative memories, medial temporal lobe (MTL) structures provide a gateway to the formation of long-term memory but are not required for short-term memory, we hypothesized that for sensorimotor memories, the cerebellum may play an analogous role. Here, we studied the sensorimotor learning of individuals with severe ataxia from cerebellar degeneration. We dissected the memories they formed during sensorimotor learning into a short-term temporally-volatile component, that decays rapidly with a time constant of just 15 to 20 s and thus cannot lead to long-term retention, and a longer-term temporally-persistent component that is stable for 60 s or more and leads to long-term retention. Remarkably, we find that these individuals display dramatically reduced levels of temporally-persistent sensorimotor memory, despite spared and even elevated levels of temporally-volatile sensorimotor memory. In particular, we find both impairment that systematically worsens with memory window duration over shorter memory windows (<12 s) and near-complete impairment of memory maintenance over longer memory windows (>25 s). This dissociation uncovers a unique role for the cerebellum as a gateway for the formation of long-term but not short-term sensorimotor memories, mirroring the role of the MTL for declarative memories. It thus reveals the existence of distinct neural substrates for short-term and long-term sensorimotor memory, and it explains both the trial-to-trial differences identified in this study and long-standing study-to-study differences in the effects of cerebellar damage on sensorimotor learning ability.
Graphene/chitosan nanoreactors for ultrafast and precise recovery and catalytic conversion of gold from electronic waste
Authors: Yang Kou , Nikolaev Konstantin G. , Li Xiaolai , Ivanov Artemii , Bong Jia Hui , Erofeev Ivan , Mirsaidov Utkur M. , Kravets Vasyl G. , Grigorenko Alexander N. , Zhang Shanqing , Qiu Xueqing , Novoselov Kostya S. , Andreeva Daria V.
Published: October 2024

The extraction of gold (Au) from electronic waste (e-waste) has both environmental impact and inherent value. Improper e-waste disposal poses environmental and health risks, entailing substantial remediation and healthcare costs. Large efforts are applied for the recovery of Au from e-waste using complex processes which include the dissolution of Au, its adsorption in an ionic state and succeeding reduction to metallic Au. These processes themselves being complex and utilizing harsh chemicals contribute to the environmental impact of e-waste. Here, we present an approach for the simultaneous recovery and reduction of Au
3+
and Au
+
ions from e-waste to produce solid Au
0
forms, thus skipping several technological steps. We develop a nanoscale cross-dimensional composite material via self-assembly of two-dimensional graphene oxide and one-dimensional chitosan macromolecules, capable of acting simultaneously as a scavenger of gold ions and as a reducing agent. Such multidimensional architecture doesn’t require to apply any voltage for Au adsorption and reduction and solely relies on the chemisorption kinetics of Au ions in the heterogeneous GO/CS nanoconfinements and their chemical reduction on multiple binding sites. The cooperative phenomena in ionic absorption are responsible for the extremely high efficiency of gold extraction. The extraction capacity reaches 16.8 g/g for Au
3+
and 6.2 g/g for Au
+
, which is ten times larger than any existing gold adsorbents can propose. The efficiency is above 99.5 wt.% (current limit is 75 wt.%) and extraction ability is down to very low concentrations of 3 ppm.
Chapter 7. Influencers’ conflictual responses to posters’ offensive comments on Instagram
Authors: Sifianou Maria , Kavroulaki Evanthia
Published: October 2024

This chapter aims to contribute to the study of Social Media Influencers’ (SMIs) discourse. More specifically, it explores the language practices of five prominent Greek SMIs, based on their responses to (perceived) impoliteness levelled against them on Instagram. After taking a close look at the acts provoking the conflictual reactions, we analysed 107 influencers’ responses to aggressive comments posted under their feed photos. Drawing on models of response options to impoliteness, we argue that the majority of SMIs who choose to respond to aggressive comments (mostly involving accusations and criticism) do so by resorting to offensive rather than defensive or mixed strategies (i.e., a combination of offensive and defensive ones), while the most salient offensive strategy used involves sarcasm. Interestingly, it seems that SMIs do not always avoid aggression to attain their strategic goals.
The artificial intelligence revolution...in unethical publishing: Will AI worsen our dysfunctional publishing system?
Authors: França Thiago F. A. , Monserrat José Maria
Published: October 2024

Scholarly publishing has been shaped by the pressure of a liquid economy to become an exercise in branding more than a vehicle for the advancement of science. The current revolution in artificial intelligence (AI) is poised to make matters worse. The new generation of large language models (LLMs) have shown impressive capabilities in text generation and are already being used to write papers, grants, peer review reports, code for analyses, and even perform literature reviews. Although these models can be used in positive ways, the metrics and pressures of academia, along with our dysfunctional publishing system, stimulate their indiscriminate and uncritical use to speed up research outputs. Thus, LLMs are likely to amplify the worst incentives of academia, greatly increasing the volume of scientific literature while diluting its quality. At present, no effective solutions are evident to overcome this grim scenario, and nothing short of a cultural revolution within academia will be needed to realign the practice of science with its traditional ideal of a rigorous search for truth.
Study of electron and positron elastic scattering cross-sections of astro molecule H2S
Authors: Meena Sunil K , Purohit Ghanshyam
Published: October 2024

The elastic, integrated, momentum transfer, viscosity, energy-dependent, and differential cross-sections and the Sherman function for electron and positron H2S scattering are reported at impact energies ranging from 1 eV to 1 MeV. The average orientations of the polar molecule H2S are considered, and the electron and positron elastic scattering cross-sections of H2S are typically calculated using single scattering-independent atom approximation. The relativistic Dirac equation is solved using the free atom optical potential, which includes the electrostatic interaction potential, exchange potential, correlation polarization potential, and imaginary absorption potential. The present computed cross-section results are compared with the available experimental and theoretical results, and a reasonable agreement is observed.