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Compared with 2019, measurements of the global growth rate of background (marine air) atmospheric methane rose by 5.3 ppb yr−1 in 2020, reaching 15.0 ppb yr−1. Global atmospheric chemistry models have previously shown that reductions in nitrogen oxide (NOx) emissions reduce levels of the hydroxyl radical (OH) and lengthen the methane lifetime. Acting in the opposite sense, reductions in carbon monoxide (CO) and non-methane volatile organic compound (NMVOC) emissions increase OH and shorten methane's lifetime. Using estimates of NOx, CO, and NMVOC emission reductions associated with COVID-19 lockdowns around the world in 2020 as well as model-derived regional and aviation sensitivities of methane to these emissions, we find that NOx emission reductions led to a 4.8 (3.8 to 5.8) ppb yr−1 increase in the global methane growth rate. Reductions in CO and NMVOC emissions partly counteracted this, changing (reducing) the methane growth rate by −1.4 (−1.1 to −1.7) ppb yr−1 (CO) and −0.5 (−0.1 to −0.9) ppb yr−1 (NMVOC), yielding a net increase of 2.9 (1.7 to 4.0) ppb yr−1. Uncertainties refer to ±1 standard deviation model ranges in sensitivities. Whilst changes in anthropogenic emissions related to COVID-19 lockdowns are probably not the only important factor that influenced methane during 2020, these results indicate that they have had a large impact and that the net effect of NOx, CO, and NMVOC emission changes can explain over half of the observed 2020 methane changes. Large uncertainties remain in both emission changes during the lockdowns and methane's response to them; nevertheless, this analysis suggests that further research into how the atmospheric composition changed over the lockdown periods will help us to interpret past methane changes and to constrain future methane projections.

Introduction: A common refrain in public health and medicine concerns the rapidly rising incidence of obesity and metabolic-like syndromes over the last two decades. A plethora of data suggests there are many roots to the issue and what to do about it. The rise of childhood obesity and the growing incidence of adult endocrine diseases like type 2 diabetes mellitus in paediatric populations are the most concerning. One of the solutions that aims to tackle health and food justice issues is the Farm-to-School programme (FTSP), which helps bring local fruit and vegetables (FVs) to schools and associated nutrition-related programmes. In the USA, a significant expansion of FTSPs has happened since the early 2000s. Numerous economic, social and nutritional benefits of these programmes have been documented, and various methodologies have been used to elucidate the benefits and barriers. Method: This paper reviews the multifaceted strengths of FTSPs including health, institutional and farm-related benefits. The paper also discusses federal- and state-level environment and the obstacles to FTSP implementation. Conclusion: FTSPs offer a comprehensive way to strengthen childhood nutrition education and stimulate local communities economically and socially. FTSPs increase the purchase of locally produced food items, resulting in higher incomes for small farmers. FTSPs have also increased community engagement and new opportunities for farming businesses. In sum, FTSPs can be considered a boon for local schools, producers, communities and better health outcomes for school-age children. Teaching children about food literacy could prove beneficial for supporting their self-efficacy regarding foods and encouraging lifetime healthy dietary behaviours.

We document the intergenerational mobility of Black and White American men from 1880 through 2000 by building new historical datasets for the late nineteenth and early twentieth century and combining them with modern data to cover the middle and late twentieth century. We find large disparities in mobility, with White children having far better chances of escaping the bottom of the distribution than Black children in every generation. This mobility gap was more important in proximately determining each generation's racial gap than was the initial gap in parents' economic status. (JEL D31, J15, J62, N31, N32)

Appinites are a suite of plutonic rocks, ranging from ultramafic to felsic in composition, that are characterized by idiomorphic hornblende as the dominant mafic mineral in all lithologies and by spectacularly diverse textures, including planar and linear magmatic fabrics, mafic pegmatites and widespread evidence of mingling between mafic and felsic compositions. These features suggest crystallization from anomalously water-rich magma which, according to limited isotopic studies, has both mantle and meteoric components.Appinites typically occur as small (~2 km diameter) complexes emplaced along the periphery of granitoid plutons and commonly adjacent to major deep crustal faults, which they preferentially exploit during their ascent. Several studies emphasize the relationship between intrusion of appinites, granitoid plutonism and termination of subduction. However, recent geochronological data suggest a more long-lived genetic relationship between appinites and granitoid magma generation and subduction.Appinites may represent aliquots of hydrous basaltic magma derived from variably fractionated mafic underplates that were originally emplaced during protracted subduction adjacent to the MOHO, triggering generation of voluminous granitoid magmas by partial melting in the overlying MASH zone. The hydrous mafic magmas from this underplate may have ascended, accumulated, and differentiated at mid-to-upper crustal levels (ca. 3-6 kbar, 15 km depth) and crystallized under water-saturated conditions. The granitoid magmas were emplaced in pulses when transient stresses activated favourably oriented structures which became conduits for magma transport. The ascent of late mafic magmas, however, is impeded by the rheological barriers created by the structurally overlying granitoid magma bodies. Magmas that form appinite complexes evaded those rheological barriers because they preferentially exploited the deep crustal faults that bounded the plutonic system. In this scenario, appinite complexes may be a direct connection to the mafic underplate and so its most mafic components may provide insights into processes that generate granitoid batholiths and, more generally, into crustal growth in arc systems.

The Paleozoic era begins with the final assembly of Gondwana and ends with the amalgamation of the supercontinent Pangea. Although this tectonic progression is generally well documented, one fundamental but under-studied phenomenon during this era is the transition from two-way to one-way (northward) migration of peripheral terranes between Gondwana and Laurentia-Baltica from Cambrian to Ordovician time. The two-way terrane accretion was likely initiated during the opening of the Rheic Ocean at ca. 510 Ma when several Gondwana-derived terranes comprising Carolinia, Ganderia, Avalonia, and Meguma sequentially drifted from the northern margin of Gondwana and eventually collided with Laurentia or Baltica. Over the same time interval, the Laurentia-derived Cuyania terrane (a.k.a., the “Precordillera terrane” is commonly believed to have accreted to the proto-Andean margin of Gondwana, whereas the peri-Laurentian/Dashwoods ribbon continent separated from, then re-accreted to, the Laurentian margin after being trapped during the collision of the Taconic arc. Alternatively, the Cuyania terrane is suggested to have remained attached to the Ouachita Embayment throughout the Cambrian–Ordovician, and then passed onto Gondwana during the collision between the proto-Andean margin and the hypothesized Texas Plateau at the leading edge of Cuyania. Here we explain the enigmatic, pene-contemporaneous migration of these peripheral terranes by a trans-Iapetus transform fault that was likely active between 510 and 450 Ma and extended from the proto-Appalachian margin of Laurentia to the proto-Andean margin of Gondwana. The trans-Iapetus transform fault terminated after the respective accretion of Carolinia and Ganderia to the proto-Appalachian margin and of Cuyania to the proto-Andean margin. We interpret the development of the trans-Iapetus transform during the Cambrian–Ordovician to be a consequence of the global geodynamic transition from the break-up of Rodinia (continents/terranes drifting away from Laurentia) to Pangea amalgamation (continents/terranes drifting toward assembling Laurussia).

Synoptic weather and larger scale circulation patterns are closely coupled and have a major influence on regional weather and extreme events. This study examines the role of regional circulations on meteorology and extreme events for the present and future years over Asia with the WRF model driven by HadGEM2 global model boundary conditions that includes RCP4.5 scenarios based bicentennial transient simulation. The regional scale analysis was based on boundary conditions derived from 40 years of global model outputs spanning periods of 1995-2005, 2015-2025, 2025-2035 and 2045-2055. For brevity these periods are labelled as 2000, 2020, 2030, 2050 and 'represent' decadal periods centered around the named years. Model results were compared and validated (using a number of skill metrics) against observations for the present period showing that the model is able to delineate the observed features within 95% confidence level compared to the annual mean. To characterise and quantify the changes in the circulation patterns, an Empirical Orthogonal Function (EOF) based analysis was conducted. Results indicate that wintertime minimum temperatures are projected to increase by 3-4 0 C over Asia by 2050 compared to reference period of 2000. Furthermore, anti-cyclonic activity associated with low PV anomalies and high positive temperature anomalies may be a key driver that influence the increase in frequency and duration of heat waves and droughts over SA, SEA, EA and NA regions of Asia. Overall, the modelling results suggest that regional meteorology and circulation patterns may significantly influence extremes over Asia in the future. Such impacts will have major implications for weather patterns as well as for air pollution over the region both of which will require policy responses to adjust to a changing regional climate.

The status of Pannotia as an Ediacaran supercontinent, or even its mere existence as a coherent large landmass, is controversial. The effect of its hypothesized amalgamation is generally ignored in mantle convection models claiming the transition from Rodinia to Pangaea represents a single supercontinent cycle. We apply three geodynamic scenarios to Pannotia amalgamation that are tested using regional geology. Scenarios involving quasi-stationary mantle convection patterns are not supported by the geological record. A scenario involving feedback between the supercontinent cycle and global mantle convection patterns predicts upwellings beneath the Gondwanan portion of Pannotia and the arrival of plumes along the entire Gondwanan (but not Laurentian) margin beginning at c. 0.6 Ga. Such a scenario is compatible with regional geology, but the candidates for plume magmatism we propose require testing by detailed geochemical and isotopic studies. If verified, this scenario could provide geodynamic explanations for the origins of the late Neoproterozoic and Early Palaeozoic Iapetus and Rheic oceans and the terranes that were repeatedly detached from their margins.

The supercontinent Pangea formed by the subduction of the Iapetus and Rheic oceans between Gondwana, Laurentia, and Baltica during mid-to-late Paleozoic times. However, there remains much debate regarding how this amalgamation was achieved. Most paleogeographic models based on paleomagnetic data argue that the juxtaposition of Gondwana and Laurussia (Laurentia-Baltica) was achieved via long-lasting highly oblique convergence in the late Paleozoic. In contrast, many geology-based reconstructions suggest that the collision between the two continents was likely initiated via a Gondwanan promontory comprising the Iberian, Armorican, and Bohemian massifs, and parts of the basement units in the Alpine orogen during the Early Devonian. To help resolve this discrepancy, we present an updated compilation of high-quality paleopoles of mid-to-late Paleozoic ages (spanning Middle Ordovician and Carboniferous times) from Gondwana, Laurentia, and Baltica. These paleopoles were evaluated with the Van der Voo selection criteria, corrected for inclination error where necessary, and were used to revise their apparent polar wander (APW) paths. The revised APW paths were constructed using an innovative approach in which age errors, A95 ovals, and Q-factors of individual paleopoles are taken into account. By combining the resulting APW paths with existing geological data and field relationships in the European Variscides, we provide mid-to-late Paleozoic paleogeographic reconstructions which indicate that the formation of Pangea was likely initiated at 400 Ma via the collision between Laurussia and a ribbon-like Gondwanan promontory that was itself formed by a scissor-like opening of the Paleotethys Ocean, and that the amalgamation culminated in the mostly orthogonal convergence between Gondwana and Laurussia.

The Earth’s mantle is currently divided into the African and Pacific domains, separated by the circum-Pacific subduction girdle, and each domain features a large low shear-wave velocity province (LLSVP) in the lower mantle. However, it remains controversial as to whether the LLSVPs have been stationary through time or dynamic, changing in response to changes in global subduction geometry. Here we compile radiogenic isotope data on plume-induced basalts from ocean islands and oceanic plateaus above the two LLSVPs that show distinct lead, neodymium and strontium isotopic compositions for the two mantle domains. The African domain shows enrichment by subducted continental material during the assembly and breakup of the supercontinent Pangaea, whereas no such feature is found in the Pacific domain. This deep-mantle geochemical dichotomy reflects the different evolutionary histories of the two domains during the Rodinia and Pangaea supercontinent cycles and thus supports a dynamic relationship between plate tectonics and deep-mantle structures. Earth’s deep-mantle domains are geochemically distinct. The African domain is enriched in subducted material, which suggests a different history from the Pacific domain and a dynamic relationship between plate tectonics and deep-mantle structures.

Continental arcs are the sites of production of continental crust, but the origin of these magmatic systems is not well understood. Although a number of processes have been suggested to be important, the role of water migrating from slab to surface during subduction has been underappreciated. Directly below the Moho, hot (approximately 1,100 °C), hydrous basaltic magmas fractionate as they cool to the regional geotherm at 750 to 800 °C, ultimately solidifying as mafic underplates. Cooling and fractionation cause water to exsolve and ascend, triggering fluid-fluxed melting of overlying mafic underplates and other crust. Melting of prior mafic underplates buffers temperatures and generates the voluminous, juvenile low-K magmas of Cordilleran batholiths. These granitoid magmas comprise a low-temperature slurry of melt and residue, and recrystallize into silicic mush during adiabatic ascent. Such hydrous mushes are intermittently infused by hotter, more mafic magmas, which hybridize and facilitate ascent and, potentially, eruption. Fluid-fluxed melting overcomes many of the general petrological and geochemical problems associated with models dominated by fractional crystallization. The role of water during repeated episodes of mafic underplating is critical to generate the juvenile granitoid infrastructure of the continents. Migration of water from the slab to the surface during subduction is highlighted as a key process in the formation of continental crust.

It is important to understand how future environmental policies will impact both climate change and air pollution. Although targeting near-term climate forcers (NTCFs), defined here as aerosols, tropospheric ozone, and precursor gases, should improve air quality, NTCF reductions will also impact climate. Prior assessments of the impact of NTCF mitigation on air quality and climate have been limited. This is related to the idealized nature of some prior studies, simplified treatment of aerosols and chemically reactive gases, as well as a lack of a sufficiently large number of models to quantify model diversity and robust responses. Here, we quantify the 2015–2055 climate and air quality effects of non-methane NTCFs using nine state-of-the-art chemistry–climate model simulations conducted for the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). Simulations are driven by two future scenarios featuring similar increases in greenhouse gases (GHGs) but with “weak” (SSP3-7.0) versus “strong” (SSP3-7.0-lowNTCF) levels of air quality control measures. As SSP3-7.0 lacks climate policy and has the highest levels of NTCFs, our results (e.g., surface warming) represent an upper bound. Unsurprisingly, we find significant improvements in air quality under NTCF mitigation (strong versus weak air quality controls). Surface fine particulate matter (PM2.5) and ozone (O3) decrease by -2.2±0.32 µg m−3 and -4.6±0.88 ppb, respectively (changes quoted here are for the entire 2015–2055 time period; uncertainty represents the 95 % confidence interval), over global land surfaces, with larger reductions in some regions including south and southeast Asia. Non-methane NTCF mitigation, however, leads to additional climate change due to the removal of aerosol which causes a net warming effect, including global mean surface temperature and precipitation increases of 0.25±0.12 K and 0.03±0.012 mm d−1, respectively. Similarly, increases in extreme weather indices, including the hottest and wettest days, also occur. Regionally, the largest warming and wetting occurs over Asia, including central and north Asia (0.66±0.20 K and 0.03±0.02 mm d−1), south Asia (0.47±0.16 K and 0.17±0.09 mm d−1), and east Asia (0.46±0.20 K and 0.15±0.06 mm d−1). Relatively large warming and wetting of the Arctic also occur at 0.59±0.36 K and 0.04±0.02 mm d−1, respectively. Similar surface warming occurs in model simulations with aerosol-only mitigation, implying weak cooling due to ozone reductions. Our findings suggest that future policies that aggressively target non-methane NTCF reductions will improve air quality but will lead to additional surface warming, particularly in Asia and the Arctic. Policies that address other NTCFs including methane, as well as carbon dioxide emissions, must also be adopted to meet climate mitigation goals.

The authors have previously proposed corrugated soft elastomeric capacitors (cSEC) to create ultra compliant scalable strain gauges. The cSEC technology has been successfully demonstrated in engineering and biomechanical applications for in-plane strain measurements. This study extends work on the cSEC to evaluate its performance at measuring angular rotation when installed folded at the junction of two plates. The objective is to characterize the sensor’s electromechanical behavior anticipating applications to the monitoring of welded connections in steel components. To do so, an electromechanical model that maps the cSEC signal to bending strain induced by angular rotation is derived and adjusted using a validated finite element model. Given the difficulty in mapping strain measurements to rotation, an algorithm termed angular rotation index (ARI) is formulated to link measurements to angular rotation directly. Experimental work is conducted on a hollow structural section (HSS) steel specimen equipped with cSECs subjected to compression to generate angular rotations at the corners within the cross-section. Results confirm that the cSEC is capable of tracking angular rotation-induced bending strain linearly, however with accuracy levels significantly lower than found over flat configurations. Nevertheless, measurements were mapped to angular rotations using the ARI, and it was found that the ARI mapped linearly to the angle of rotation, with an accuracy of 0.416∘.

Compared to 2019, the global growth rate of atmospheric methane rose by about 50 % in 2020, reaching 15 ppb/yr. Models of global atmospheric chemistry show that reductions in nitrogen oxide (NOx) emissions reduce levels of the hydroxyl radical, and lengthen the methane lifetime. Using estimates of NOx emission reductions associated with COVID-19 lockdowns around the world in 2020, together with model-derived regional and sectoral sensitivities of methane to NOx emissions, we find that NOx emissions reductions can fully explain the observed surge in the global methane growth rate. Whilst changes in NOx emissions are probably not the only important factor that has influenced methane since the beginning of 2020, it is clear that they are a key factor that will need to be included within any attribution study, and that they may well be the dominant driver of these recent methane changes. The major global scale changes in composition of the Earth’s atmosphere measured during lockdown provide unprecedented constraints on the sensitivity of the atmospheric chemical system to changes in emissions, and are of great utility for evaluating policy-relevant models.

This study integrates sedimentological and stratigraphic insights into the Upper Permian sedimentary rocks of the Wittingham, Tomago and Newcastle Coal Measures in the Northern Sydney Basin, Australia. Facies analysis documented fifteen facies that belong to seven facies associations. These facies associations correspond to different depositional environments and sub-environments including prodelta, delta-front, upper, lower delta-plain and fluvial. The stratigraphic development points to a shallowing upward trend and is reflected with fluvial deposits sitting on top of the deltaic deposits. The fluvio-deltaic contact is represented by an unconformity and displays an upward increase in sediment caliber. The delta front is mainly controlled by wave, storms- and/or river currents, even though the contribution of tides also occurs in the form of sedimentary structures that suggest tidal influence. In contrast, prodelta and delta-plain are significantly modulated by tidal currents. The impact of tides in the delta plain is fading away upward and therefore, the upper delta plain is much less impacted compared to the lower delta plain. The low abundance of wave ripples suggests that the wave action was not very important in the delta plain. Steep topographic gradients and increased sediment input are suggested, based on the limited or absent evidence of tides in the fluvial realm, related to the growing New England Orogen. In sequence stratigraphic terms, the deltaic system accumulated during highstand normal regression, while the deposition of the overlying fluvial system occurred during lowstand normal regression. The two systems are separated by a subaerial unconformity developed during an intervening forced regression. Short periods of transgression are inferred from the presence of higher frequency cycles in the delta-front.

An observationally-constrained time series of historical aerosol effective radiative forcing (ERF) from 1750 to 2019 is developed in this paper. We find that the time history of aerosol ERFs diagnosed in CMIP6 models exhibits considerable variation and explore how the time history of aerosol forcing influences the probability distributions of present-day aerosol forcing and emergent metrics such as climate sensitivity. Using a simple energy balance model, trained on CMIP6 climate models and constrained by observed near-surface warming and ocean heat uptake, we derive estimates for the historical aerosol forcing. We find 2005-2014 mean aerosol ERF to be -1.1 (-1.8 to -0.5) W m-2 relative to 1750. Assuming recently published historical emissions from fossil fuel and industrial sectors and biomass burning emissions from SSP2-4.5, aerosol ERF in 2019 is -0.9 (-1.5 to -0.4) W m-2. There is a modest recovery in aerosol forcing (+0.025 W m-2 decade-1) between 1980 and 2014. This analysis also gives a 5-95% range of equilibrium climate sensitivity (ECS) of 1.8-5.1°C (best estimate 3.1°C) with a transient climate response (TCR) of 1.2-2.6°C (best estimate 1.8°C).

Designers have long recognized the inherent structural efficiency and economy associated with non-redundant bridge systems. Presently, steel bridge structures with non-redundant tension members, labeled as fracture critical members (FCMs), are subjected to more stringent design, material, fabrication, and inspection requirements. FCM requirements are contained in the AASHTO/AWS Fracture Control Plan (FCP) and Code of Federal Regulations (CFRs). The consequence of the requirements, in particular as related to the associated in-service inspection costs, is a higher life-cycle cost when compared to redundant steel bridge structures. However, significant advances have been made over the past 40 years since the original AASHTO/AWS FCP was introduced. Advances in the understanding of fracture mechanics, material and structural behavior, and fatigue crack initiation and growth as well as advancements in fabrication and inspection technologies have allowed other industries to address fracture in a more integrated manner. One-step toward an integrated FCP is to take advantage of the superior fracture toughness of modern steels. While increased fracture toughness is a performance benefit often highlighted for modern steels, there is a lack of fundamental test data and material characterization studies. A large test program was conducted focused on the use of high-toughness steels routinely used in bridge fabrication to establish rational inspection intervals for members traditionally classified as fracture critical. The project was comprised of small-scale material testing, full-scale fracture testing of steel bridge axial and bending members, three-dimensional finite element modeling, and an analytical parametric study. Material characterization results, which included tensile testing, chemistry, Charpy v-notch (CVN) impact testing, percent shear measurement, reference temperature determination, and ductile tearing initiation testing, are presented. Test results showed some of the steels tested demonstrated larger than expected CVN scatter in the transition region. Most importantly, the research revealed for the steels tested the master curve created using Charpy-sized SE(B) specimens resulted in an overestimate of fracture toughness compared to 1 T SE(B) specimens.

The classical S–I–A-type granites from the Lachlan Orogen, SE Australia, formed as a tectonic end-member of the accretionary orogenic spectrum, the Paleozoic Tasmanides. The sequence of S-to I-to A-type granite is repeated at least three times. All the granites are syn-extensional, formed in a dominantly back-arc setting behind a single, stepwise-retreating arc system between 530 and 230 Ma. Peralkaline granites are rare. Systematic S–I–A progressions indicate the progressive dilution of an old crustal component as magmatism evolved from arc (S-type) to proximal back-arc (I-type) to distal back-arc (A-type) magmatism. The alkaline and peralkaline A-type Younger granites of Nigeria were generally hotter and drier than the Lachlan A-type granites and were emplaced into an anhydrous Precambrian basement during intermittent intracontinental rifting. This geodynamic environment contrasts with the distal back-arc setting of the Lachlan A-type granites, where magmatism migrated rapidly across the orogen. Tectonic discrimination diagrams are inappropriate for the Lachlan granites, placing them in the wrong settings. Only the peralkaline Narraburra suite of the Lachlan Orogen fits the genuine ‘within-plate’ setting of the Nigerian A-type granites. Such discrimination diagrams require re-evaluation in the light of an improved modern understanding of tectonic processes, particularly the role of extensional tectonism and its geodynamic drivers.

The proto-Andean margin of Argentina consists of several suspect terranes, the origins of which are disputed. The Cuyania (greater Precordillera) suspect terrane was originally interpreted to be of southeast Laurentian affinity, but more recently a southwestern Gondwanan provenance has been argued. Both potential source regions comprise Mesoproterozoic rocks, but we show they are isotopically distinct, using previously published zircon Lu-Hf data. Detrital zircon εHf data from southwestern Gondwana (Namaqua-Natal belt) show no correlation with new zircon U-Pb and Lu-Hf data from Cuyania, suggesting that Gondwana was not the source of these sediments. Rather, detrital zircons from Cambrian strata in Cuyania yield Mesoproterozoic zircons with depleted εHf that correlate to the Grenville margin of Laurentia, and a ca. 535 Ma zircon population sourced directly from rift-related rocks of the Ouachita Embayment, thus recording rifting and drifting of Cuyania from Laurentia. By contrast, zircons from Middle to Late Ordovician strata of Cuyania record a larger range of εHf values, correlated with Western Sierras Pampeanas Mesoproterozoic basement inliers of Argentina. These synorogenic clastic deposits record the Ordovician arrival of Cuyania at the proto-Andean margin of Gondwana. The new data require the terrane boundaries of Cuyania to be redefined, thereby excluding Western Sierras Pampeanas basement inliers. The results verify the Laurentian microcontinent model for the origin of Cuyania.

An integrated study of sedimentological, sequence-stratigraphic and palaeodispersal analysis was applied to the Upper-Permian clastic sedimentary succession in the Northern Sydney Basin, Australia. The succession is subdivided into fifteen facies and three facies associations. The facies associations are further subdivided into eight sub-facies associations. The sedimentary evolution involves progradation from delta-front to delta-plain to fluvial depositional environments, with a significant increase in sediment grain size across the unconformable contact that separates the deltaic from the overlying fluvial system. In contrast to the delta front that is wave/storm- and/or river-influenced, the delta plain is significantly affected by tides, with the impact of tidal currents decreasing up-sequence in the delta plain. The general lack of wave-influenced sedimentary structures suggests low wave energy in the delta plain. The abrupt termination of the tidal impact in the fluvial realm relates to the steep topographic gradients and high sediment supply, which accompanied the uplift of the New England Orogen. The sequence-stratigraphic framework includes highstand (deltaic forest and topset) and lowstand (fluvial topset) systems tracts, separated by a subaerial unconformity. In contrast to most of the mud-rich modern counterparts, this is an example of a sand-rich tidally influenced deltaic system, developed adjacent to the source region. This investigation presents a depositional model for tidal successions in regions of tectonic uplift and confinement.

Distortion-induced fatigue cracking in aging steel bridges is a primary concern for many bridge owners and stakeholders, accounting for the majority of fatigue cracks in bridges in the United States. Currently Departments of Transportation primarily use visual inspections to locate and characterize fatigue cracks. However, this approach has drawbacks, as recent studies have shown that visual inspections are not able to consistently identify realistically-sized fatigue cracks in highway infrastructure. Additionally, it requires significant time and cost to perform visual inspections, and both inspectors and the traveling public are placed at risk during the inspection. Bridge owners and stakeholders would benefit from the development of inspection techniques that do not rely on hands-on human visual inspection – to reduce the risks of harm to the inspectors and traveling public, increase reliability, and decrease the time and cost of performing inspections. Vision-based technologies are an active area of research in the field of structural health monitoring, aimed at developing alternatives to manual inspection for identifying damage to transportation infrastructure. The majority of these studies have focused on macro-indicators of damage, including identifying excessive corrosion, concrete deck deterioration, and large displacements due to substructure movement. Digital image correlation (DIC) is one such vision-based technology that shows promise for detecting and characterizing fatigue cracks, but investigations and applications have thus far been limited to simple, in-plane cracking. Three-dimensional DIC measurements have the ability to capture full-field displacements and surface strains, allowing for the potential of identifying and characterizing out-of-plane fatigue cracks, such as those occurring on steel bridges exposed to loading through differential girder displacement. Since the majority of fatigue cracks arise from out-of-plane loading, investigating the efficacy of DIC for detecting distortion-induced fatigue cracks is of clear value. This paper describes an experimental study in which a scaled steel girder-to-cross-frame specimen was cyclically loaded to produce geometrically complex distortion-induced fatigue cracking. To examine the potential usefulness of DIC for future automated bridge inspections the resulting fatigue cracks were characterized using DIC and visual inspection. The methodology applied proved successful at quantifying certain aspects of the complex, bifurcating cracks, but had difficulty characterizing crack segments that are no longer actively loaded. Additional work is needed to improve the accuracy and reliability of the crack detection results for this technology to potentially be used as an automated inspection tool in the future.

Fatigue cracking is a major concern for many aging steel bridges in the United States. A common form of crack remediation is the drilling of crack-arrest holes, increasing the crack tip radius and thus reducing the applied stress intensity. However, the majority of cracking that occurs in bridge structures is caused by distortion-induced fatigue. Cross-frame forces generated by differential girder displacement produce multiaxial, mixed-mode fatigue loading at the intersection of the girder web, flange, and connection plate, producing cracking along web-to-stiffener welds and flange-to-web welds. Crack-arrest holes are often used as a first line of defense at these cracks. However, crack-arrest holes deform out-of-plane under distortion-induced fatigue loading, and have been found to be of limited utility in this application. Previous research has shown that mechanical treatment of crack-arrest holes has the potential to improve the efficacy of crack-arrest holes for halting crack propagation for in-plane fatigue, but the performance of such treatments is unknown for distortion-induced fatigue cracks. A research program sponsored by the Kansas Department of Transportation is investigating the effectiveness of one such technology for controlling crack propagation in steel bridge girders susceptible to distortion-induced fatigue. This technology produces a cold-worked region around the crack-arrest hole, introducing a field of compressive residual stresses aimed at retarding crack propagation. Evaluation of the mechanically treated crack-arrest holes is evaluated analytically for both in-plane and out-of-plane fatigue loading. This paper presents background on the problem and preliminary findings of the study.

Welded-wire reinforcement (WWR) is widely used as the main reinforcement in bridge decks and vertical shear reinforcement in concrete bridge girders. Previous studies on concrete members re...

We investigate a novel use of model nudging to interrogate radiative rapid adjustment mechanisms and their magnitudes in response to aerosol emission perturbations in an earth system model. The radiative effects of a forcing agent can be quantified using the effective radiative forcing (ERF). ERF is the sum of the instantaneous radiative forcing, and radiative adjustments – changes in the atmosphere’s state in response to the initial forcing agent that cause a further radiative forcing. Radiative adjustments are particularly important for aerosols, which affect clouds both via microphysical interactions and changes in circulation, stratification and convection. Understanding the different adjustment mechanisms and their contribution to the total ERF of different aerosol emissions is necessary to better understand how their ERF may change with future changes in anthropogenic aerosol emissions. In this work we investigate radiative adjustments resulting from changes in atmospheric temperature (and the resulting changes in stratification and convection) due to anthropogenic sulphate and black carbon aerosol forcing.We have conducted multiple global atmosphere-only time-slice experiments using the UK Earth System Model (UKESM1). Each experiment has either control, black carbon perturbed, or sulphur dioxide perturbed emissions; and either no nudging, nudged horizontal winds (uv), or nudged horizontal winds and potential temperature (uvθ). The difference between nudged uvθ minus nudged uv simulations determines the atmospheric temperature related adjustments arising from the aerosol perturbation. We have also conducted repeats of each simulation, varying the nudging setup to test sensitivity to different nudging parameters.We find that nudging horizontal winds affects the resulting ERF very little, whereas nudging potential temperature as well can cause a significant difference from the non-nudged experiments, primarily in the cloud radiative effect. However, this difference is sensitive to the strength of the nudging applied, for which we consider the most appropriate value.