bluuebunny/crossref_metadata_2025 huggingface dataset:
Enabling highly efficient and broadband electromagnetic wave absorption by tuning impedance match in high-entropy transition metal diborides (HE TMB2)
Authors: Zhang Weiming , Dai Fu-Zhi , Xiang Huimin , Zhao Biao , Wang Xiaohui , Ni Na , Karre Rajamallu , Wu Shijiang , Zhou Yanchun
Published: September 2021

The advance in communication technology has triggered worldwide concern on electromagnetic wave pollution. To cope with this challenge, exploring high-performance electromagnetic (EM) wave absorbing materials with dielectric and magnetic losses coupling is urgently required. Of the EM wave absorbers, transition metal diborides (TMB2) possess excellent dielectric loss capability. However, akin to other single dielectric materials, poor impedance match leads to inferior performance. High-entropy engineering is expected to be effective in tailoring the balance between dielectric and magnetic losses through compositional design. Herein, three HE TMB2 powders with nominal equimolar TM including HE TMB2-1 (TM = Zr, Hf, Nb, Ta), HE TMB2-2 (TM = Ti, Zr, Hf, Nb, Ta), and HE TMB2-3 (TM = Cr, Zr, Hf, Nb, Ta) have been designed and prepared by one-step boro/carbothermal reduction. As a result of synergistic effects of strong attenuation capability and impedance match, HE TMB2-1 shows much improved performance with the optimal minimum reflection loss (RLmin) of −59.6 dB (8.48 GHz, 2.68 mm) and effective absorption bandwidth (EAB) of 7.6 GHz (2.3 mm). Most impressively, incorporating Cr in HE TMB2-3 greatly improves the impedance match over 1–18 GHz, thus achieving the RLmin of −56.2 dB (8.48 GHz, 2.63 mm) and the EAB of 11.0 GHz (2.2 mm), which is superior to most other EM wave absorbing materials. This work reveals that constructing high-entropy compounds, especially by incorporating magnetic elements, is effectual in tailoring the impedance match for highly conductive compounds, i.e., tuning electrical conductivity and boosting magnetic loss to realize highly efficient and broadband EM wave absorption with dielectric and magnetic coupling in single-phase materials.
Experimental study and comparison of different fully transparent laminated glass beam designs
Authors: Centelles Xavier , Castro J. Ramon , Pelayo F. , Aenlle-López Manuel , Cabeza Luisa F.
Published: September 2021

Laminated glass beams without metallic or polymeric reinforcements generally lack post-breakage strength and ductility. This paper aims to perform a comparative study by testing five different fully transparent laminated glass beam designs in order to see how parameters such as the number and thickness of glass sheets (3 x 10 mm or 5 x 6 mm), the interlayer material (PVB Clear or SentryGlas), and the thermal treatment of glass (annealed or heat-strengthened) affect the pre-breakage performance and post-breakage safety. A buckling analysis is also performed using a numerical model with ABAQUS CAE. The study includes a comparison between the results of different experimental mechanical tests on laminated glass beams, including the tests presented in this paper, as well as other tests found in the literature. All designs presented a linear elastic behaviour until initial breakage. The interlayer material mainly affected the crack shape of laminated glass beams. Beams with five sheets of annealed glass had a more progressive breakage, and therefore a safer behaviour, than beams with three sheets of annealed or heat-strengthened glass.
Mothers in Mind: Exploring the Efficacy of a Dyadic Group Parenting Intervention for Women Who Have Experienced Intimate Partner Violence and Their Young Children
Authors: Jenney Angelique , Scott Katreena , Wall Michael
Published: September 2021

Identifying and responding to the mental health needs of young children (0–4 years) exposed to intimate partner violence is one of the most pressing issues confronting child mental health and welfare sectors today. Children exposed to IPV (CEIPV) are at an increased risk of experiencing maltreatment, developing emotional and behavioral problems, and experiencing other adversities (Kimball, Journal of Family Violence, 31, 625–637, 2016). Among the range of protective factors that can mitigate against this impact is a strong relationship with, and attachment to, a primary caregiver (Holt, Buckley, & Whelan, Child Abuse & Neglect, 32, 797–810, 2008). Despite this, there are few evidenced-based programs which address the unique parenting supports required by women who experience domestic violence, while simultaneously attending to the unique developmental and psycho-social needs of exposed young children (Austin, Shanahan, Barrios, & Macy, Trauma, Violence and Abuse, 20(4), 498–519, 2019). This article describes the development and preliminary evaluation of Mothers in Mind, a trauma-informed, dyadic, mother–child intervention program designed to meet this need. Analyses of data from 36 mother–child dyads who completed pre- and post-group evaluation find that, after program completion, mothers report greater parenting self-efficacy, healthier parenting, and enhanced psychological well-being. The importance of relational capacity building in mother–child dyads impacted by violence and suggestions for future avenues for research and intervention are explored.
Establishing Healthy Personal Hygiene Habits with Young Children in Australia: A Cross-Sectional Mixed Methods Study
Authors: Mitchell Amy E. , Kulasinghe Kavindri , Morawska Alina
Published: September 2021

Effective and consistent engagement in personal hygiene practices is important for preventing the acquisition and transmission of communicable diseases in childhood. This study aimed to investigate trends in adherence to recommended hygiene practices and identify factors contributing to difficulties in establishing good hygiene habits with young children (0–4 years) in Australia. A self-selected community sample of parents (N = 426) completed an online survey assessing children's adherence to recommended hygiene practices and barriers and enablers of establishing good personal hygiene habits. Parents reported interest in receiving information/tips on children's personal hygiene (yes/no) and nominated topics of interest. Less than half of children in any age group consistently (always/almost always) covered coughs and sneezes, washed hands after toileting, or washed hands before meals or when dirty. Children's non-compliance (i.e. resistance, refusal) was the most commonly reported barrier to establishing good personal hygiene habits, while children's compliance (i.e. cooperative behaviour, following or complying with caregivers’ instructions) was the most commonly cited enabler. Despite low levels of adherence, less than half (41.2%) of parents wanted information/tips on children's hygiene. Results suggest a disconnect between parents’ knowledge about recommended hygiene practices and actual behaviour. Development and testing of approaches to behaviour change that incorporate evidence-based strategies to manage children's resistance and support parents to encourage the development of healthy hygiene habits is warranted.
Stochastic properties of generalized finite mixture models with dependent components
Authors: Amini-Seresht Ebrahim , Balakrishnan Narayanaswamy
Published: September 2021

In this paper we consider a new generalized finite mixture model formed by dependent and identically distributed (d.i.d.) components. We then establish results for the comparisons of lifetimes of two such generalized finite mixture models in two different cases: (i) when the two mixture models are formed from two random vectors
$\textbf{X}$
and
$\textbf{Y}$
but with the same weights, and (ii) when the two mixture models are formed with the same random vectors but with different weights. Because the lifetimes of k-out-of-n systems and coherent systems are special cases of the mixture model considered, we used the established results to compare the lifetimes of k-out-of-n systems and coherent systems with respect to the reversed hazard rate and hazard rate orderings.
Telephone clinic outcomes during the coronavirus disease 2019 pandemic: results from an ENT department
Authors: Mallick S , Balakumar R , Drysdale A
Published: September 2021

Objective

To study the impact of telemedicine on patient outcomes during a nationwide lockdown to halt the spread of coronavirus disease 2019.

Methods

A retrospective study was conducted to examine telemedicine consultations of newly referred patients over 7 days during a national lockdown. Overall outcomes of telephone clinics were recorded, measured as either patient discharged, imaging requested, patient referred to another specialty, further telephone follow up required, patient initiated follow up or face-to-face appointment required.

Results

Data were collected from 104 patients. Outcomes showed that 17 patients were discharged, 15 had imaging requested, 11 were referred to another specialty, 11 had further telemedicine appointments, 31 had patient-initiated follow up and 19 received face-to-face appointments. Overall, 57 per cent of patients avoided hospital visits and 17 per cent required face-to-face appointments. Of higher risk patients, 49 per cent were managed remotely. After eight months, no significant morbidity or mortality was reported.

Conclusion

Almost half of the higher risk patients avoided a hospital visit. The majority of patients were managed remotely, and thus the risk and spread of infection were reduced. Telemedicine has an important role in ENT out-patients.
Use of a dissected intravenous giving set to assist large metal oesophageal foreign body removal in rigid oesophagoscopy
Authors: Robinson M , Pankhania R , Pelser A , Bowles P
Published: September 2021

Background

Oesophageal foreign body removal may be challenging. If a foreign body is sufficiently high risk and cannot be retrieved via oesophagoscopy, laparotomy may be required as the foreign body migrates distally.

Objective

This paper presents the use of the plastic tubing from an intravenous giving set, combined with rigid oesophagoscopy grasping forceps, in order to improve purchase and obtain sufficient traction on a large, smooth, metallic distal oesophageal foreign body (knife).

Results and conclusion

This method offers an option for removal of oesophageal foreign bodies that may be rendered challenging with traditional metal grasping forceps given the lack of purchase and traction afforded by a ‘metal on metal’ grip, potentially avoiding the need for open surgery.
How children learn to communicate discriminatively
Authors: RAMSCAR Michael
Published: September 2021

How do children learn to communicate, and what do they learn? Traditionally, most theories have taken an associative, compositional approach to these questions, supposing children acquire an inventory of form-meaning associations, and procedures for composing / decomposing them; into / from messages in production and comprehension. This paper presents an alternative account of human communication and its acquisition based on the systematic, discriminative approach embodied in psychological and computational models of learning, and formally described by communication theory. It describes how discriminative learning theory offers an alternative perspective on the way that systems of semantic cues are conditioned onto communicative codes, while information theory provides a very different view of the nature of the codes themselves. It shows how the distributional properties of languages satisfy the communicative requirements described in information theory, enabling language learners to align their expectations despite the vastly different levels of experience among language users, and to master communication systems far more abstract than linguistic intuitions traditionally assume. Topics reviewed include morphological development, the acquisition of verb argument structures, and the functions of linguistic systems that have proven to be stumbling blocks for compositional theories: grammatical gender and personal names.
Are surgical and non-operating room intervention safe in the COVID-19 pandemic? A retrospective study
Authors: Aktas Yildirim Serap , Sarikaya Zeynep Tugce , Ulugol Halim , Ozata Sanem , Aksu Ugur , Toraman Fevzi ,   COVID-19 Study Group
Published: September 2021

Little is known about the impact of COVID-19 on the outcomes of patients undergoing surgery and intervention. This study was conducted between 20 March and 20 May 2020 in six hospitals in Istanbul, and aimed to investigate the effects of surgery and intervention on COVID-19 disease progression, intensive care (ICU) need, mortality and virus transmission to patients and healthcare workers. Patients were examined in three groups: group I underwent emergency surgery, group II had an emergency non-operating room intervention, and group III received inpatient COVID-19 treatment but did not have surgery or undergo intervention. Mortality rates, mechanical ventilation needs and rates of admission to the ICU were compared between the three groups. During this period, patient and healthcare worker transmissions were recorded. In total, 1273 surgical, 476 non-operating room intervention patients and 1884 COVID-19 inpatients were examined. The rate of ICU requirement among patients who had surgery was nearly twice that for inpatients and intervention patients, but there was no difference in mortality between the groups. The overall mortality rates were 2.3% in surgical patients, 3.3% in intervention patients and 3% in inpatients. COVID-19 polymerase chain reaction positivity among hospital workers was 2.4%. Only 3.3% of infected frontline healthcare workers were anaesthesiologists. No deaths occurred among infected healthcare workers. We conclude that emergency surgery and non-operating room interventions during the pandemic period do not increase postoperative mortality and can be performed with low transmission rates.
Europe without Borders: Environmental and Global History in a World after Continents
Authors: Frank Johnson Alison
Published: September 2021

In 2012 the historian Julia Adeney Thomas restrained her temper but unleashed a warning. The occasion was a forum in the American Historical Review on ‘historiographic “turns” in critical perspective’. The perspectives offered were critical enough, Thomas wrote in praise of the other authors, but the forum had a blind spot: ‘alongside the turns analyzed here, a world-altering force has been emerging, one larger, more devastating, and more definitive even than “contemporary flexible forms of capitalism”: I speak of climate change – or climate collapse – and all of its related global transformations’. Since then, some intersectional scholars have gone beyond that to argue that climate collapse and racial capitalism are not separate topics at all, but are bound together by white supremacy and lingering forms of European imperialism. Over the past decade some environmental historians have grappled with these connections and deployed new frameworks for thinking about scale, the interdependence of the local and the global, the implications of a Euro-centric analytical framework for our understanding of the world and the relationship between economic systems and environmental change. Although they have developed separately, both environmental history and global history have called upon historians of Europe to rethink boundary making in their methodologies and in their categories of analysis. In an era of global climate catastrophe, global pandemic and global economic crisis, where does the ‘European’ environment end?
Improving Disaster Data Systems to Inform Disaster Risk Reduction and Resilience Building in Australia: A Comparison of Databases
Authors: Cuthbertson Joseph , Archer Frank , Robertson Andy , Rodriguez-Llanes Jose M.
Published: September 2021

Objective:

Disaster impact databases are important resources for informing research, policy, and decision making. Therefore, understanding the underpinning methodology of data collection used by the databases, how they differ, and quality indicators of the data recorded is essential in ensuring that their use as reference points is valid.

Methods:

The Australian Disaster Resilience Knowledge Hub (AIDRKH) is an open-source platform supported by government to inform disaster management practice. A comparative descriptive review of the Disaster Mapper (hosted at AIDRKH) and the international Emergency Events Database (EM-DAT) was undertaken to identify differences in how Australian disasters are captured and measured.

Results:

The results show substantial variation in identification and classification of disasters across hazard impacts and hazard types and a lack of data structure for the systematic reporting of contextual and impact variables.

Conclusions:

These differences may have implications for reporting, academic analysis, and thus knowledge management informing disaster prevention and response policy or plans. Consistency in reporting methods based on international classification standards is recommended to improve the validity and usefulness of this Australian database.
Investment Decisions on Physical Activity Promotion: A Locality Case Study in Complex Public Health Policy Making
Authors: Whitelaw Sandy , Topping Chris
Published: September 2021

The role of ‘best investment’ methodology in shaping priorities in many health policy areas is becoming increasingly prominent. Whilst this has traditionally been seen as a technocratic exercise, the social and political context of such practices and the constructed nature of decisions are now considered significant. In this context, this article reports on a longitudinal case study of such a process that sought to identify ‘best investments’ in public health interventions related to promoting physical activity. Drawing on a series of conceptual resources, we describe and reflect upon the complex and invested elements that contributed to the grounded decision-making process. In conclusion we suggest the need to adopt a multifaceted and nuanced approach to resource investment decision making, including: deploying a range of appraisal assessment resources; maintaining a long-term processual perspective; involving a variety of stakeholders; accepting and embracing fallibility; and accommodating theoretical and empirical evidence-based principles.
Hidden depths: diversity, difference and the High Court of Australia
Authors: Cahill-O'Callaghan Rachel , Roberts Heather
Published: September 2021

There is a growing international emphasis on the importance of diversity in the judiciary and the impact of the individual in decision-making. However, it can be a challenge to gain insight into the individuals who sit on the bench. For instance, there is limited official information about the individuals who sit on the High Court of Australia. One of the rare glimpses provided by the justices themselves is their judicial swearing-in speech. Drawing on a case-study of the swearing-in speeches of High Court justices sitting between 2008 and 2016, this paper illustrates how these speeches can illuminate key demographic information about the judiciary, as well as facets of the individual rarely explored in studies of judicial diversity: personality and values. This study demonstrates how swearing-in speeches can assist with filling information gaps about judicial diversity, and so extend debates about judicial selection.
Individual Differences and Changes in Self-Reported Work Performance During the Early Stages of the COVID-19 Pandemic
Authors: Zacher Hannes , Rudolph Cort W. , Posch Melina
Published: September 2021

Abstract. This longitudinal study examines how three dimensions of self-reported work performance, including task proficiency, adaptivity, and proactivity, changed between December 2019 and September 2020 in Germany. Based on event system and transition theories, we expected work performance to decline because of the “lockdown” between early April and early May 2020 and to subsequently increase when restrictions were eased between early May and early September 2020. Additionally, we hypothesized that high levels of core self-evaluations (i. e., employees’ fundamental evaluations about themselves) buffer the decline and strengthen the recovery in work performance. Data were collected from N = 591 full-time employees across eight measurement points. Results based on discontinuous latent growth curve modeling largely supported the expected trajectories in work performance. Moreover, core self-evaluations positively predicted the levels of work performance as well as the slopes indicating recovery in task proficiency and adaptivity, but not proactivity.
Something Old or Something New?
Authors: Klostermann Marina , Ontrup Greta , Thomaschewski Lisa , Kluge Annette
Published: September 2021

Abstract. In 2020, the COVID-19 pandemic forced organizations to adjust co-located teams to virtual teams instantly. The applicability of known success factors for virtual teamwork to this situation is uncertain. Therefore, this study addresses the following research question: what factors relate to successful team adjustment to the new virtual work context? We hypothesize that perceived team success is influenced by individual and team factors and that these effects of team-related factors on perceived team success are moderated by team processes and team-/task-technology fit. A time-lagged online study was conducted at two timepoints during the initial lockdown in Germany with N = 110 employees working in teams. We found trust, task-technology fit, and communication to be significantly associated with perceived team performance. The results suggest that the instant adjustment might have led to a new phase related to team cycle episodes. We propose guidelines to prepare teams for future instant adjustments.
The Impact of Telework and Closure of Educational and Childcare Facilities on Working People During COVID-19
Authors: Rieth Michèle , Hagemann Vera
Published: September 2021

Abstract. This study examines the impact of telework and closure of educational and childcare facilities on working people during COVID-19. We compare telework versus nontelework conditions and people with and without stay-at-home children. Data from 465 working people in Germany were collected via an online survey. People who do not work from home experience more stress, more negative and less positive affect, less life satisfaction and trust in government, and less loss of control over career success than those working from home. Concerning the conservation of resources theory, working from home can thus be seen as a resource gain, representing, in accordance with the self-regulation theory, a way to deal with pandemic threats. However, home office only seems to be beneficial if working conditions at home are supportive; otherwise, it is experienced as a resource threat or loss, especially with stay-at-home children.
Potential of Clumped Isotopes in Constraining the Global Atmospheric Methane Budget
Authors: Chung Edward , Arnold Tim
Published: September 2021

Atmospheric methane (CH4) and its isotopic composition trends over the last decades are explained by various flux scenarios, from tropical wetland emission increases through to reductions in global hydroxyl (OH). In this study, we develop a modeling framework to assess the potential usefulness of clumped isotope measurements to distinguish between the main drivers of change in the CH4 burden. We model interhemispheric differences of 0.12‰ and 0.38‰ and seasonal cycles of 0.02‰–0.04‰ and 0.21‰–0.32‰ for Δ13CH3D and Δ12CH2D2, respectively, which is insignificant relative to the uncertainty of measurements that could eventually be made. We show, however, that measurements of Δ12CH2D2 specifically could provide constraints for understanding trends in the global total source and sink magnitudes, which has not been possible with the current sets of observables. Changes in OH concentration of 10% developed across three decades result in a difference of up to 2‰ in Δ12CH2D2, which would be observable given current measurement uncertainty limits. For this type of global‐scale analysis, we show that measurements of Δ13CH3D would be unlikely to provide additional useful information. We suggest an emphasis should now be on developing the methods to make measurements from ambient air samples, followed by measurements of Δ13CH3D and Δ12CH2D2 from sampling at clean Northern and Southern Hemisphere sites, combined with more accurate and precise laboratory measurements of the clumped kinetic isotope effects relevant for the atmospheric sinks.
The Surface Energy Budget at Gale Crater During the First 2500 Sols of the Mars Science Laboratory Mission
Authors: Martínez G. M. , Vicente‐Retortillo A. , Vasavada A. R. , Newman C. E. , Fischer E. , Rennó N. O. , Savijärvi H. , de la Torre M. , Ordóñez‐Etxeberria I. , Lemmon M. T. , Guzewich S. D. , McConnochie T. H. , Sebastián E. , Hueso R. , Sánchez‐Lavega A.
Published: September 2021

We use in situ environmental measurements by the Mars Science Laboratory (MSL) mission to obtain the surface energy budget (SEB) across Curiosity's traverse during the first 2500 sols of the mission. This includes values of the downwelling shortwave solar radiation, the upwelling solar radiation reflected by the surface, the downwelling longwave radiation from the atmosphere, the upwelling longwave radiation emitted by the surface, the sensible heat flux associated with turbulent motions, and the latent heat flux associated with water phase changes. We then analyze their temporal variation on different timescales and relate this to the mechanisms causing these variations. Through its Rover Environmental Monitoring Station, MSL allows for a more accurate determination of the SEB than its predecessors on Mars. Moreover, the unprecedented duration, cadence, and frequency of MSL environmental observations allow for analyses of the SEB from diurnal to interannual timescales. The results presented in this article can be used to evaluate the consistency with predictions from atmospheric numerical models, to validate aerosol radiative properties under a range of dust conditions, to understand the energy available for solar‐powered missions, and to enable comparisons with measurements of the SEB by the Perseverance rover at Jezero crater.
Achieving Equilibrium as a Semi‐Alluvial Channel: Anthropogenic, Bedrock, and Colluvial Controls on the White Clay Creek, PA, USA
Authors: Bodek Sophie , Pizzuto James E. , McCarthy Kristen E. , Affinito Raphael A.
Published: September 2021

Based on well‐developed hydraulic geometry relations for width and depth, classic studies initially interpreted the Mid‐Atlantic White Clay Creek (WCC) as a quasi‐equilibrium, alluvial channel. Subsequent studies document the legacy of colonial‐age watershed disturbances and urban development, confounding earlier classifications. To investigate this matter, we contribute new data from reach‐scale geomorphic mapping, and observations and modeling of bed material transport. WCC's longitudinal profile reflects a history of bedrock incision, while hydraulic geometry equations for width and depth indicate quasi‐equilibrium cross‐sectional adjustment. Alluvial landforms such as pools and riffles, bars, and actively forming floodplains occur at all 12 study sites, but exposures of bedrock and colluvium are also common. The ratio of bankfull to threshold Shields stress averages 1.41 (range: 0.41–2.63), suggesting that WCC is an alluvial, threshold, gravel‐bed river. However, a numerical model of WCC bed material transport and grain size, calibrated to bedload tracer data, demonstrates that 22% (range: 8%–73%) of bed material is composed of immobile, locally sourced cobbles and boulders, while the remaining bed material represents mobile, sand to cobble‐sized alluvium; this leads us to classify WCC as a semi‐alluvial river. Additional computations suggest that channel morphology is insensitive to bed material supply. Field observations imply that bankfull Shields stresses do not represent channel adjustments to achieve stable banks; rather, width adjustment likely reflects cohesive bank processes. Despite the numerous and contradictory labels applied to WCC (i.e., quasi‐equilibrium, Anthropocene, bedrock, semi‐alluvial, and gravel‐bed), each term contributes insight that any single conceptual model would be unable to provide alone.
Beyond the Mass Balance: Watershed Phosphorus Legacies and the Evolution of the Current Water Quality Policy Challenge
Authors: Van Meter K. J. , McLeod M. M. , Liu J. , Tenkouano G. Thierry , Hall R. I. , Van Cappellen P. , Basu N. B.
Published: September 2021

Increased use of phosphorus (P) fertilizers and detergents and intensified livestock production have more than doubled P inputs to human‐impacted watersheds over pre‐industrial levels. While P fertilizer use and manure application help to maximize crop yields, excess P is lost to runoff, leading to eutrophication of downstream waters. Excess P also accumulates across the landscape, leading to legacies that serve as long‐term sources of P to surface waters, even after inputs to the watershed are reduced. Here, we have developed, for the first time, a process‐based model, Exploration of Long‐tErM Nutrient Trajectories‐Phosphorus, designed to capture legacy P accumulation and depletion trajectories along the land‐aquatic continuum. To drive the model, we have developed a more than 100‐year trajectory of watershed P inputs to the Grand River Watershed (GRW), Canada’s largest watershed draining directly to Lake Erie. Our results first show that net P inputs to the watershed approximately tripled between 1900 and the late‐1970s, when P surplus magnitudes peaked at approximately 15 kg ha−1 y−1. During this same period, stream P loads have increased more than fourfold, from 0.11 kg ha−1 y−1 in 1900 to 0.80 kg ha−1 y−1 in the 1970s. Since 1900, the GRW has served as a net P sink, with approximately 96% of net P inputs having been retained within the basin. Future simulations suggest that while 40% reductions in P loading in Lake Erie watersheds are possible under aggressive management scenarios, legacy P will continue to elevate P loads to Lake Erie for many decades to come.
A Preliminary Regional Geomorphologic Map in Utopia Planitia of the Tianwen‐1 Zhurong Landing Region
Authors: Mills Mackenzie M. , McEwen Alfred S. , Okubo Chris H.
Published: September 2021

A geomorphologic map is an important step to understanding the geologic context and history of a site; here, we present an initial geomorphologic map for an area spanning 22°–26°N, 108°–112°E in the Utopia Planitia (UP) region on Mars. This site is of special interest because it contains the May 2021 landing site of the Zhurong rover from Tianwen‐1. Utopia Planitia exhibits many lobate features that have been proposed to be lava or mud flows. Lander and rover data should help solve the scientific question concerning the origin of UP flows. We use our map to generate an initial stratigraphic framework of geomorphological features in order to help place future Zhurong data into the regional geologic context. Our mapping effort has detailed the distribution of three geomorphologic units and 11 types of surface features.
Statistical Distribution of Decameter Scale (50 m) Ionospheric Irregularities at High Latitudes
Authors: Jin Yaqi , Clausen Lasse B. N. , Spicher Andres , Ivarsen Magnus F. , Zhang Yongliang , Miloch Wojciech J. , Moen Jøran I.
Published: September 2021

We present a study of decameter scale ionospheric irregularities using in‐situ electron density data from the NorSat‐1 satellite. During the current period of low solar activity, NorSat‐1 frequently observes significant plasma irregularities from several 10 s km down to several decameter. These are often observed near the dayside cusp and dawnside auroral zone. The decameter‐scale irregularities are positively correlated with intermediate‐scale (10 km) density gradients, for both negative and positive gradients encountered by the satellite. The statistical distribution of electron density over two winter months in the northern hemisphere along NorSat‐1 orbits, shows significant density increases in the cusp ionosphere (75°–80° Magnetic LATitude) and in regions near the dawnside auroral oval. Intermediate scale density gradients and small‐scale irregularities are clearly associated with these density enhancements. We postulate that these density enhancements and irregularities are due to auroral particle precipitation/plasma dynamics.
Alternatives to Liquid Water Beneath the South Polar Ice Cap of Mars
Authors: Schroeder Dustin M. , Steinbrügge Gregor
Published: September 2021

Radar sounding of Mars’ south polar ice cap has revealed portions of its base with stronger radar returns than its surface. These have been used to estimate high real permittivity values consistent with liquid water. However, the thermal, chemical, and geological conditions required to sustain such water bodies are challenging to achieve in the contemporary Martian environment. Three recent papers address this conflict. Khuller and Plaut (2021, https://doi.org/10.1029/2021GL093631) find similar radar signatures across the ice cap, expanding the range conditions associated with water candidates. Bierson et al. (2021, https://doi.org/10.1029/2021GL093880) show that, for non‐zero conductivity, a wider range of materials could produce the observed echoes. Similarly, Smith et al., (2021, https://doi.org/10.1029/2021GL093618) use modeling, laboratory tests, and remote sensing data to propose smectite deposits as their specific source. While not incompatible with bodies of liquid brines, these papers provide potential alternative sources for the bright radar observations.
Scale Dependence of Earthquake Rupture Prestress in Models With Enhanced Weakening: Implications for Event Statistics and Inferences of Fault Stress
Authors: Lambert Valère , Lapusta Nadia , Faulkner Daniel
Published: September 2021

Determining conditions for earthquake slip on faults is a key goal of fault mechanics highly relevant to seismic hazard. Previous studies have demonstrated that enhanced dynamic weakening (EDW) can lead to dynamic rupture of faults with much lower shear stress than required for rupture nucleation. We study the stress conditions before earthquake ruptures of different sizes that spontaneously evolve in numerical simulations of earthquake sequences on rate‐and‐state faults with EDW due to thermal pressurization of pore fluids. We find that average shear stress right before dynamic rupture (aka shear prestress) systematically varies with the rupture size. The smallest ruptures have prestress comparable to the local shear stress required for nucleation. Larger ruptures weaken the fault more, propagate over increasingly under‐stressed areas due to dynamic stress concentration, and result in progressively lower average prestress over the entire rupture. The effect is more significant in fault models with more efficient EDW. We find that, as a result, fault models with more efficient weakening produce fewer small events and result in systematically lower b‐values of the frequency‐magnitude event distributions. The findings (a) illustrate that large earthquakes can occur on faults that appear not to be critically stressed compared to stresses required for slip nucleation; (b) highlight the importance of finite‐fault modeling in relating the local friction behavior determined in the lab to the field scale; and (c) suggest that paucity of small events or seismic quiescence may be the observational indication of mature faults that operate under low shear stress due to EDW.
Adjoint‐State Traveltime Tomography for Azimuthally Anisotropic Media and Insight Into the Crustal Structure of Central California Near Parkfield
Authors: Tong Ping
Published: September 2021

Seismic anisotropy provides crucial information on the stress state and geodynamic processes inside the Earth. We develop a novel adjoint‐state traveltime tomography method using P‐wave traveltime data to simultaneously determine velocity heterogeneity and azimuthal anisotropy of the subsurface. First, an anisotropic eikonal equation is derived to model first‐arrival traveltimes in azimuthally anisotropic media. Traveltime tomography is then formulated as an optimization problem constrained by the anisotropic eikonal equation, which is subsequently solved by the adjoint‐state method. Ray tracing is not required. Its high accuracy is achieved by solving the anisotropic eikonal equation and the associated adjoint equation with efficient numerical solvers. In addition, an eikonal equation‐based earthquake location method for azimuthally anisotropic media is developed to solve the coupled hypocenter‐velocity problem. The tomography and earthquake location methods are applied to central California near Parkfield to test their performance in practice. A total of 1,068,850 first P‐wave traveltimes clearly maps the velocity heterogeneity and azimuthal anisotropy in the upper and middle crust. The average P‐wave velocity model shows a striking velocity contrast across the San Andreas Fault (SAF). In the upper crust, we find structural anisotropy in the SAF zone and stress‐induced anisotropy off the SAF zone. In the middle crust, the fast P‐wave velocity directions are generally fault‐parallel due to the decreased effect of the maximum horizontal compressive stress. In all, the real‐data application suggests that the new adjoint‐state traveltime tomography method can be reliably used to investigate anisotropic seismic structures.
Deciphering Fine Electrical Conductivity Structures in the Crust From MT Data Using the Equivalent Conductivity Formula
Authors: Liu Shuyu , Xu Yixian , Yang Bo , Guo Zeqiu , Shi Yuan , Liu Ying
Published: September 2021

Fine structures in the lower crust sounded by seismic reflection can be formed in various geological processes and their electrical resistivity properties can provide significant insights into the geodynamic processes of the lithosphere. The magnetotelluric (MT) method is popular for imaging the electrical resistivity structure of the lithosphere; however, it lacks high resolution to resolve the small heterogeneities in deep crust. To recover the fine electrical resistivity structures, we propose a strategy based on their equivalent resistivity that defines the relationship between the fine structures and the inverted bulk resistivities. Thus, we first formulated the equivalent resistivity for a 3‐D laminated structure with >95% accuracy. In this strategy, the bulk resistivity inverted from MT data is used to retrieve the fine resistivity structures, for which the corresponding equivalent resistivities should match with the inverted resistivities. The strategy was tested to demonstrate its feasibility for analyzing the electrical property and the cause of lamellae in the lower crust of the Basin and Range Province. From the bulk resistivities of 1‐D anisotropic inversion, we retrieved the resistivity of lamellae that was in the range of 0.15–0.3  and coincident with the resistivity of silicate melts, implying that the lamellae are probably magma chambers with >50% melt fraction, which is also supported by seismic and geological evidences. Our case study demonstrated that this strategy based on equivalence can be successfully used to recover the fine resistivity structures from MT data.
A Driftwood‐Based Record of Arctic Sea Ice During the Last 500 Years From Northern Svalbard Reveals Sea Ice Dynamics in the Arctic Ocean and Arctic Peripheral Seas
Authors: Hole Georgia M. , Rawson Thomas , Farnsworth Wesley R. , Schomacker Anders , Ingólfsson Ólafur , Macias‐Fauria Marc
Published: September 2021

We present a 500‐year history of naturally felled driftwood incursion to northern Svalbard, directly reflecting regional sea ice conditions and Arctic Ocean circulation. Provenance and age determinations by dendrochronology and wood anatomy provide insights into Arctic Ocean currents and climatic conditions at a fine spatial resolution, as crossdating with reference chronologies from the circum‐Arctic boreal forests enables determination of the watershed the driftwood originated from. Sample crossdating may result in a wide range of matches across the pan‐boreal region, which may be biased toward regions covered by the reference chronologies. Our study considers alternate approaches to selecting probable origin sites, by weighting scores via reference chronology span and visualizing results through spatiotemporal density plots, as opposed to more basic ranking systems. As our samples come from naturally felled trees (not logged or both), the relative proportions of different provenances are used to infer past ocean current dominance. Our record indicates centennial‐to decadal‐scale shifts in source regions for driftwood incursion to Svalbard, aligning with Late Holocene high variability and high frequency shifts in the Transpolar Drift and Beaufort Gyre strengths and associated ﬂuctuating climate conditions. Driftwood occurrence and provenance also track the northward ice formation shift in peripheral Arctic seas in the past century. A distinct decrease in driftwood incursion during the last 30 years matches the observed decline in pan‐Arctic sea ice extent in recent decades. Our new approach successfully employs driftwood as a proxy for Arctic Ocean surface circulation and sea ice dynamics.
Is the Relationship Between Stratospheric Arctic Vortex and Arctic Oscillation Steady?
Authors: Hu Dingzhu , Guan Zhaoyong , Liu Meichen , Wang Tao
Published: September 2021

The connections between the stratosphere and troposphere, for example, the stratospheric Arctic vortex (SAV) and Arctic Oscillation (AO), have been paid attention by scientists and the public in recent years. Previous studies suggested that the coupling between the stratosphere and troposphere is the strongest in winter. However, whether the link between SAV and AO during boreal winter on interannual timescales is steady is still unknown. Our results show that the interannual relationship between the SAV in early winter and AO in late winter during 1958–2018 is unsteady and has experienced a remarkable interdecadal change around the 2000s, with large and statistically significant positive correlations before the 2000s but small and insignificant correlations after the 2000s. The weakened linkage between the SAV and AO after the 2000s is possibly caused by (a) the weakened downward effect of SAV on the North Atlantic and polar sectors of AO, and (b) the opposite signs of sea level pressure (SLP) in the North Pacific and North Atlantic. The links of SAV‐AO are enforced (weakened) when AO‐related SLP anomalies over the North Pacific are the same (opposite) signs of those over the North Atlantic before (after) the 2000s. Differences in the tropospheric state over the North Pacific during two periods might be jointly contributed by the SAV and the SAV‐related significant (insignificant) sea surface temperature anomalies over central North Pacific in the earlier (latter) period. Our results may provide evidences to improve the predictability in seasonal or interannual timescales forecasts of weather and climate at mid‐latitudes.
Effects of the June 2018 Global Dust Storm on the Atmospheric Composition of the Martian Upper Atmosphere as Observed by MAVEN
Authors: Farahat Ashraf , Mayyasi Majd , Withers Paul , Dayeh Maher A. , Abuelgasim Abdelgadir
Published: September 2021

The densities of six neutral species in the Martian upper atmosphere were analyzed before and during the 2018 Martian global dust storm (GDS 2018) using data from the Neutral Gas and Ion Mass Spectrometer of the Mars Atmosphere and Volatile EvolutioN mission. The trends of the dayside densities of the neutral species and their relative abundances were investigated between May 27 and June 17, 2018, at altitudes of 160–210 km. GDS 2018 caused variations in the neutral species abundance of the upper atmosphere at its onset in June 5–8, 2018, with the CO2, Ar, CO, O, N2, and He densities decreasing relative to prestorm conditions. The densities of the examined neutral species increased during the storm, except those of O and He. During the storm, the relative abundances of CO2 and Ar increased, while those of CO and O decreased and those of N2 and He remained the same. The variation in the neutral species with altitude was consistent with the regular atmospheric conditions and unrelated to the GDS 2018 drivers. The higher thermospheric temperature observed during the storm onset suggested that changes in the composition of the neutral species were caused by storm‐induced thermal enhancements.
From Sugar to Flowers: A Transition of Shallow Cumulus Organization During ATOMIC
Authors: Narenpitak Pornampai , Kazil Jan , Yamaguchi Takanobu , Quinn Patricia , Feingold Graham
Published: September 2021

The Atlantic Tradewind Ocean‐Atmosphere Mesoscale Interaction Campaign (ATOMIC) took place in January–February, 2020. It was designed to understand the relationship between shallow convection and the large‐scale environment in the trade‐wind regime. A Lagrangian large eddy simulation, following the trajectory of a boundary‐layer airmass, can reproduce a transition of trade cumulus organization from “sugar” to “flower” clouds with cold pools, observed on February 2–3. The simulation is driven with reanalysis large‐scale meteorology, and in‐situ aerosol data from ATOMIC and its joint field study EUREC4A. During the transition, large‐scale upward motion deepens the cloud layer. The total water path and optical depth increase, especially in the moist regions where flowers aggregate. This is due to mesoscale circulation that renders a net convergence of total water in the already moist and cloudy regions, strengthening the organization. An additional simulation shows that stronger large scale upward motion reinforces the mesoscale circulation and accelerates the organization process by strengthening the cloud‐layer mesoscale buoyant turbulence kinetic energy production.
Operational Multi‐GNSS Global Ionosphere Maps at GFZ Derived From Uncombined Code and Phase Observations
Authors: Brack Andreas , Männel Benjamin , Wickert Jens , Schuh Harald
Published: September 2021

Global navigation satellite system (GNSS) networks with multi‐frequency data can be used to monitor the activity of the Earth's ionosphere and to generate global maps of the vertical total electron content (VTEC). This article introduces and evaluates operational GFZ VTEC maps. The processing is based on a rigorous least squares approach using uncombined code and phase observations, and does not entail leveling techniques. A single‐layer model with a spherical harmonic VTEC representation is used. The solutions are generated in a daily post‐processing mode with GPS, GLONASS, and Galileo data, and are provided for the period since the beginning of 2000. A comparison of the GFZ VTEC maps with the final combined International GNSS Service (IGS) product shows a high consistency with the solutions of the IGS analysis centers. A validation with about four years of Jason‐3 altimetry‐derived VTEC data is provided, in which the GFZ solution has the smallest bias of 1.2 TEC units compared to the solutions of the IGS analysis centers, and with 3.0 TEC units one of the smallest standard deviations.