Background Forest succession is an important ecological process and has been studied for more than a century. However, changes in nitrogen (N) availability during succession remain unclear as they may lead to either N saturation or N limitation. Here, we propose a conceptual model to illustrate changes in N availability during four stages of secondary succession using the natural abundance of ¹⁵ N in plant leaves (foliar δ ¹⁵ N). We predicted that N availability would decline in the early stages of succession and then increase in late stages, coinciding with the changes in foliar δ ¹⁵ N, with the inflection point varying in different climate zones. Data on foliar δ ¹⁵ N from 16 succession sequences were synthesized to explore changes in N availability during forest succession. Results The compiled data were consistent with the proposed conceptual model. Foliar δ ¹⁵ N in boreal and temperate forests decreased significantly in the first two stages of succession (estimated to last at least 66 years in temperate forests), at a rate of 0.18‰ and 0.38‰ per decade, respectively, and decreased slightly in tropical forests in the first 23 years. Foliar δ ¹⁵ N is projected to increase in later stages in all forests, which is supported by observations in both temperate and tropical forests. The inflection points of N availability when N limitation peaked during succession were different in different climate zones, implying different ecosystem N turnovers. Conclusions Our study reconciles the controversies regarding changes in N availability during forest secondary succession. Our findings are also useful for predicting the recovery of N and carbon accumulation during succession. Nonetheless, studies on forest secondary succession using foliar δ ¹⁵ N have thus far been limited, and more research should be conducted to further verify the conceptual model proposed here.
Task-unrelated thoughts (TUTs) are frequent distractions from our everyday tasks, which can reduce productivity and safety during task performance. This necessitates the examination of factors that modulate TUT occurrence in daily life. One factor that has previously been implicated as a source of TUT is personally salient concerns. External factors such as news media serve as cues for these concerns, potentially increasing TUT occurrence. However, this has not been thoroughly examined in everyday life settings. We thus utilized Ecological Momentary Assessment to survey participants throughout the day for ten days, on their TUTs and news consumption in two separate studies. Study 1 focused on the impact of news related to the Coronavirus Disease (COVID-19) pandemic, as a common and global concern. We found that TUT occurrence was significantly predicted by COVID-19 news consumption, such that TUT occurrence increased with COVID-19 news consumption. To extend these findings, we implemented Study 2 using similar methods, but focusing on the consumption of news media in general. TUT occurrence was predicted by general news consumption, with an increase in reports of TUT following consumption of news media in general. We thus extended the association found between TUT and COVID-19-related news in Study 1, to any news topic in Study 2. We speculate that the increase in TUTs was due to heightened salience of current concerns, cued by the news. These findings highlight the importance of considering when we choose to consume news media and the value of examining contextual factors when studying TUTs in daily life.
Drawing upon the Brands as Intentional Agents Framework, this study investigates the impact of claim specificity of green advertising on consumers’ reactions toward the brand, and reveals a double-edged effect of claim specificity that depends on the dimensions of the brand’s image (perceived competence/warmth). Through two experiments, we show that the positive effect of claim specificity depends on the brand competence level, and that brand warmth interacts with brand competence, such that claim specificity can backfire and lower consumers’ attitudes and purchase intentions when brand warmth and competence are both low. This interactive effect is serially mediated by the perceived manipulative intent and perceived environmental commitment of the brand. Our research contributes to the literature on corporate social responsibility (CSR) communication by providing a nuanced picture of the effects of claim specificity, and offers guidance for companies on how to communicate more effectively about their CSR activities.
Small-scale, residential solar systems have been increasingly recognized as a key sector for future carbon emission reduction in cities. This study investigated customer preferences of solar thermal and photovoltaic systems through a crowdsourced discrete choice experiment and latent class choice modeling targeting Boston, Massachusetts and Atlanta, Georgia. Key motivating factors for adoption in both testbeds are installation cost, environmental benefits, and annual savings. Despite the latent classes’ similarity in their preferences of different system features, all classes present different socioeconomic characteristics across the two testbeds, indicating preference heterogeneity across cities. We also found that both cities have significant early adopters residing in lower-property-value regions, revealing a potential to achieve both carbon emission reduction and community renaissance objectives when combining infrastructure renovation projects with decentralized energy systems installation. This study presents a framework for assessing and understanding the social demand of decentralized energy systems to facilitate their future promotions.
For the past three decades, polar-orbiting ocean color satellites have provided local, regional to global scale estimates of oceanic net primary production that have greatly aided studies of ocean carbon cycling, food web dynamics and climate change. Despite considerable progress, accurate estimates of daily ocean productivity from space have not been realized because polar-orbiting satellites are unable to account for variations in phytoplankton physiology and carbon fixation rates from changing incident irradiance levels over the course of the day. Here we have attempted to exploit the unique short-temporal measurements provided by the Korean Geostationary Ocean Color Imager (GOCI), to obtain for the first time, diurnal and daily measurements of surface- and euphotic-column integrated Net Primary Productivity (NPP). These estimates are based on the Absorption Based Productivity Model (AbPM), and are calibrated with a bio-optical database of measurements made at different times of the day during the Korea-US Ocean Color (KORUS-OC) cruise in May–June 2016. Photo-physiological rate estimates, varied across different water types encountered around the Korean Peninsula, but on account of their limited number, were regionally scaled through the use of dynamic optical-biogeochemical (O-BGC) Biomes. Comparisons of GOCI derived estimates of daily and weekly integrated NPP against in-situ measurements, clearly underscore the superiority of geostationary over polar-orbiting ocean color satellites, which consider the strong short-term fluctuations in phytoplankton light absorption and incident irradiance fields over the course of the day.
One of the many outcomes of the COVID-19 pandemic was a shift in the delivery of elementary (primary) education. Schools transitioned swiftly to e-learning and prioritized education that was already or could be easily adapted to virtual formats. Given the paucity of online content available, it is not likely that child sexual abuse (CSA) prevention education was prioritized. Given that CSA prevention education has demonstrated success in increasing knowledge, protective behaviors, and disclosures, and the potential long-term need for e-learning options, there is a demand for an exploration of how CSA prevention can be implemented using e-learning strategies. In the current discussion, we explore how school-based CSA prevention education could be implemented in a “new normal” context of e-learning. We first present the existing e-learning content for CSA prevention education. We then describe how best practices for prevention education can be applied to e-learning. Finally, we present considerations for the use of e-learning specifically for CSA prevention education. In short, implementing CSA prevention programs through e-learning offers many affordances for program accessibility and reach, flexibility in implementation and opportunities for greater exposure to content, and a wide range of ways to demonstrate effective skills and engage children in cycles of practice and feedback. E-learning, may also, however, limit important conversations between children and trained instructors that lead to disclosures. The extant literature leaves us unsure as to whether implementing CSA prevention programs through e-learning will result in better or worse outcomes for children. However, given the increasing demand for e-learning options, and the promise of some new e-learning programs, further research on the effectiveness of e-learning CSA prevention programs is warranted.
This paper presents complementary analytical analyses, experiments, and numerical simulations of the electromagnetic tube compression (EMTC) process using a multi-turn axisymmetric coil with a field shaper. In earlier contributions, we proposed an analytical model capable of predicting the magnetic pressure, radial velocity, and radial displacement for EMTC. In the present paper, our understanding of EMTC is expanded with the aid of a modified analytical model, a series of experimental tests with various materials, and 3D coupled electromagnetic-mechanical numerical simulations. First, the analytical model was improved by generating elements across the entire landing area of the field shaper. This modification provided a more accurate induced magnetic pressure in the analytical model. In addition, the experimentally measured coupling coefficients between the coil, field shaper, and workpiece tube were directly incorporated into the analytical model as opposed to utilizing them as correction factors during the magnetic pressure calculation in the previous studies. In the proposed analytical model, at each time increment, the magnetic field geometry is updated in response to the tube deformation. Second, to assess the proposed analytical model, experimental tests with Photon Doppler Velocimetry (PDV) were carried out for three different materials with different thermo-mechanical properties, i.e., Al6061-T6, Cu101, and Cu260 (Brass). Third, to compare the computational cost of the analytical model and to determine the accuracy of the proposed analytical model compared to the existing software packages in the market, a 3D coupled electromagnetic-mechanical finite element model was used. To investigate the influence of discharge energy on tube deformation, all three methods were examined at three different charging energies, i.e., 2.4, 3.6, and 4.8 kJ. Reasonably good agreement between all three approaches validates the ability of the analytical model to accurately capture the deformation velocity and displacement for this complex multi-physics manufacturing process in a computationally cost-effective manner. Such an analytical model can be used as a base model for predicting the impact velocity during electromagnetic pulse welding and crimping processes prior to performing expensive and time-consuming experimental tests or numerical simulations.
Research on international joint ventures (IJVs) has paid increasing attention to the context of emerging markets (EMs). While the intersection of the IJV and EM research streams has grown, it has overlooked the effects of the partner firm home country and IJV host country context on the IJV outcome. In this study, we develop a typology of IJVs based on home and host countries as either developed or emerging markets to address this gap. Using a dataset of 24,011 IJVs in 48 countries between 1995 and 2017, we examine the impact of partners’ home countries, the IJV host country, and their interactions on the likelihood of IJV termination. Our findings reveal that beyond the frequently examined partner-, IJV-, and host country-related factors in prior research, the context of IJV partners’ home countries, the IJV host country, and their interactions significantly matter for IJV termination.
Recent discoveries of significant variations in stable K isotope ratios (⁴¹K/³⁹K or δ41K) among various terrestrial samples indicate that K isotopes can be a novel tracer for the global K cycle, but a key observation that seawater δ41K is ∼0.6‰ higher than the bulk silicate Earth remains unexplained. An unconstrained component critical to this puzzle is hydrothermal systems that represent both a major K source and sink in the ocean. Here we report δ41K results on mid-ocean ridge (MOR) hydrothermal fluids from the Gorda Ridge and ∼9°N East Pacific Rise (EPR), including time-series samples that recorded major perturbations in fluid chemistry induced by a local volcanic eruption. Fluid δ41K values range from -0.46‰ to -0.15‰, falling between those of fresh basalts and seawater. δ41K values of “time-zero” fluids collected shortly after the volcanic eruption are shifted towards the seawater value, followed by a return to pre-eruption values within ∼2 years. Fluid δ41K variations are largely influenced by water–rock interactions, but they cannot be solely explained by simple mixing of seawater and K leached from basalts at high temperatures. Instead, these data imply small but significant isotope fractionation that enriches heavy K isotopes in basalts, likely caused by low-temperature alteration during the recharge stage of hydrothermal circulation. Our results preclude MOR hydrothermal systems as the cause for the heavy δ41K value of seawater. Using fluid δ41K data and K isotope fractionation constrained here for hydrothermal systems, a K mass-balance model implies a critical role for a marine sedimentary sink, possibly authigenic clay formation, in the global K cycle. Also, applying the K isotope fractionation constrained here to the published δ41K data from ophiolites shows the possibility for significantly lower seawater δ41K during the Ordovician, which can be explained by enhanced reverse weathering in response to distinct climate and tectonics at that time.
Linguists interested in intonation have long struggled to establish a maximally broad set of annotation conventions that function equally well across varieties of American English. The current study tests the advantages and limitations of the widely-used MAE-ToBI conventions, focusing on the H* and L+H* distinction, for three varieties of American English: African American English, Appalachian English, and Jewish English. Results of quantitative analysis of production data from 30 speakers of the three varieties finds major differences in rate of use of the H* and L+H* pitch accent as well as the phonetic realizations of these pitch accents, which may not be captured solely using the MAE-ToBI conventions. These differences appear not only between MAE-ToBI and the other three varieties, but also between the varieties themselves in unique ways that may shed light on the nature of sociolinguistic variation at the level of intonation, as well as the debated status of the distinction of H* vs. L+H* as a phonological or phonetic distinction. These findings provide further motivation for the development and use of annotation systems that explicitly consider sociolinguistic variation as well as phonetic parameters. Such systems will become even more essential as both sociolinguists and phoneticians expand intonational analysis beyond so-called “standard varieties” in order to arrive at a richer and more accurate picture of the intonational system of American English.
Phenomenologists usually insist that their approach involves going “back” to and “starting” with technoscientific experience—that is, returning to the actual existing or living through of technoscientific life—after centuries of privileging the analysis of how things are “objectively” known and denigrating accounts of how they are “subjectively” lived with. But then who says this and how is this understood? “Who” is really a phenomenologist, when so many diverse thinkers claim the title? This paper considers some of the reasons why this is such a difficult question and argues that it is wrong to look for The Answer to it.
Experimental data are reported for a wind turbine array boundary layer (WTABL) in a model wind farm. An array of 95 model wind turbines consisting of 5 streamwise columns by 19 spanwise rows was studied in a high Reynolds number boundary layer in the Flow Physics Facility (FPF) at the University of New Hampshire. The wind turbine array was constructed of porous disks of 0.25 m diameter, which were drag (thrust) matched to typical offshore wind turbine operating conditions. The turbine spacing was 8 diameters in the streamwise and 4 diameters in the spanwise directions. Spires were used to thicken the boundary layer and achieve a boundary layer thickness on the order of 1 m at the first row of the wind turbine array, which is located 33 m downstream from the test section inlet, thus placing the turbines in the bottom 1/3 of the boundary layer. Velocity profiles were measured with a pitot tube in the center column of the array. To within experimental uncertainty, a fully developed WTABL condition is observed in the mean velocity, for defined inlet conditions and spacings, from row 12 on. The wind turbine array acts as a sparse displaced roughness: it creates an internal layer whose origin (in the wall‐normal direction) remains fixed in space, while the turbulent boundary layer the array was placed in continues to grow. Careful consideration was given to an expanded uncertainty analysis, which elucidates the need for long measurement times in large facilities. Porous disk turbine models are the experimental equivalent of numerical actuator disks; therefore, this publicly available data set is expected to be useful for numerical model validation.
In this study, we draw on the threatened egotism theory to examine the effect of angel narcissism on their investment behaviors and the boundary condition of past investment performance. We propose that angel narcissism is positively related to deal size and portfolio industry diversification but negatively related to the number of co-investors. Moreover, past investment performance moderates these relationships such that the effects of angel narcissism on their investment behaviors are stronger when past investment performance is lower. Data from a longitudinal analysis of 133 angels from 2010 to 2019 largely supported our hypotheses. Our study, the first to examine angel narcissism, highlights the psychological foundation of angel investing.
Expansive soils are generally characterized by their volume change when subjected to variation in water content. This may result in significant damage to supported and nearby structures. In this study, the swelling properties of bentonite material as an expansive soil are first determined. The expansive soil is then improved using two different approaches, namely, micro-metakaolin and ferric chloride solution. The optimum percentage for both additives are determined using laboratory experiments. These percentages are found to be 25% and 1% for the micro-metakaolin and the ferric chloride solution, respectively. The free swell index of the bentonite after being treated with micro-metakaolin and ferric chloride solution at the optimum percentages are found to decrease by about 54% and 62%, respectively. Meanwhile, the swelling pressure for the expansive soil decreased by 33% and 43% when mixed with the same optimum values of micro-metakaolin and ferric chloride solution, respectively. Based on the results obtained in this study, the addition of ferric chloride solution achieved better results compared to micro-metakaolin. This improvement technique may be used to enhance the properties of expansive soils that support different construction engineering projects.
Intelligent management of power and spectrum is the most important ingredient in creating wireless sensor networks with high reliability and longevity. The main application under study in this paper is accurate monitoring of forest ecosystems using high spatio-temporal resolution. High cost of the current systems and their power consumption limits wide spread use of these systems limiting the accuracy of current models. This project utilizes artificial intelligence and machine learning to learn the changes in the wireless network and environment, producing power efficient systems that are low cost to enable large scale monitoring. The proposed system was built at the University of Maine’s Wireless Sensor Networks (WiSe-Net) laboratory in collaboration with University of New Hampshire and University of Vermont researchers for soil moisture measurement with provision to include other sensor types at later stages.
Compared with gradual climate change, extreme climatic events have more direct and dramatic impacts on vegetation growth. However, the influence of climate extremes on important phenological periods, such as the end of the growing season (EOS), remains unclear. Here, we investigate the temporal trends of EOS across different biomes and quantify the response of EOS to multiple climate extreme indices (CEIs). Northern middle and high latitudes. 2000–2020. Plants. Three phenology extraction methods were used to compute EOS from satellite, FLUXNET and Pan European Phenology Project PEP725 phenological datasets. Different stress states of cold, hot, dry and wet extremes were represented by 12 CEIs. Partial correlation and ridge regression analysis were used to quantify the response of EOS to climate extremes across latitudinal and biome scales. Our study showed a delayed EOS in boreal biomes, but a significantly advanced EOS in temperate biomes. The advanced EOS induced by cold stress was observed for c. 80% of the vegetated pixels. The warm‐related CEIs delayed the EOS in high latitudes, and the delayed effect weakened or even reversed with decreasing latitude. In contrast, EOS exhibited opposite response patterns to dry days and wet‐related CEIs. Overall, EOS exhibited higher sensitivity to extreme temperature in boreal biomes than in temperate biomes. Specifically, continuous drought and high heat stress induced an earlier EOS in some temperate forest biomes, whereas moderate heat stress delayed the EOS in most study biomes. In contrast, EOS was not sensitive to extreme drought in water‐restricted biomes. EOS exhibited divergent responses to various climate extremes with different intensities and frequencies. Moreover, the response of EOS to extreme climate stress was dependent on the biome and latitude. These findings emphasize the importance of incorporating the divergent extreme climate effects into vegetation phenological models and Earth system models.
Occasionally, lightning will exit the top of a thunderstorm and connect to the lower edge of space, forming a gigantic jet. Here, we report on observations of a negative gigantic jet that transferred an extraordinary amount of charge between the troposphere and ionosphere (∼300 C). It occurred in unusual circumstances, emerging from an area of weak convection. As the discharge ascended from the cloud top, tens of very high frequency (VHF) radio sources were detected from 22 to 45 km altitude, while simultaneous optical emissions (777.4 nm OI emitted from lightning leaders) remained near cloud top (15 to 20 km altitude). This implies that the high-altitude VHF sources were produced by streamers and the streamer discharge activity can extend all the way from near cloud top to the ionosphere. The simultaneous three-dimensional radio and optical data indicate that VHF lightning networks detect emissions from streamer corona rather than the leader channel, which has broad implications to lightning physics beyond that of gigantic jets.
Global magnetospheric effects resulting from the passage at Earth of large-scale structures have been well studied. The effects of common and short-term features, such as discontinuities and current sheets (CSs), have not been studied in the same depth. Herein we show how a seemingly unremarkable interplanetary feature can cause widespread effects in the magnetosheath-magnetosphere system. The feature was observed by Advanced Composition Explorer inside an interplanetary coronal mass ejection on 10 January 2004. It contained 1) a magnetic field dip bounded by directional discontinuities in field and flows, occurring together with 2) a density peak in what we identify as a bifurcated, non-reconnecting current sheet. Data from an array of spacecraft in key regions of the magnetosheath/magnetosphere ( Geotail, Cluster, Polar, and Defense Meteorological Satellite Program ) provide context for Wind’s observations of flapping of the distant (R ∼ −226 R E ) magnetotail. In particular, just before the flapping began, Wind observed a hot and tenuous plasma in a magnetic field structure with enhanced field strength, with the By and Bz components rotating in a fast tailward flow burst. Closer inspection reveals a large flux rope (plasmoid) containing lobe plasma in a tail strongly deflected and twisted by interplanetary non-radial flows and magnetic field By . We try to identify the origin of this ‘precursor to flapping’ by looking at data from the various spacecraft. Working back towards the dayside, we discover a chain of effects which we argue were set in motion by the interplanetary CS and its interaction with the bow shock. These effects include 1) a compression and dilation of the magnetosphere, 2) a local deformation of the postnoon magnetopause, and, 3) at the poleward edge of the oval in an otherwise quiet polar cap flow, a strong (3 km/s) sunward flow burst in a double vortex-like structure flanked by two sets of field-aligned currents. Clearly, an intertwined set of phenomena was occurring at the same time. We learn that multi-spacecraft analysis can give us great insight into the magnetospheric response to transient changes in the solar wind.
The burden of obesity and chronic disease is increasing in the older US Hispanic/Latino adult population. There is limited evidence on successful weight management strategies as perceived by this population. Assessing barriers and opportunities for weight management using mixed methods is a robust approach to collect in‐depth information that can be applied to the development of well‐tailored weight management interventions for this population. The objective of this study was to assess perceived individual, interpersonal, and environmental factors that influence weight management in older Hispanic/Latino adults. This community‐based cross‐sectional study included 23 Hispanic/Latino older (>50y) adults with obesity (BMI >30kg/m2). Perceived barriers and opportunities for weight management were assessed through validated questionnaires and focus groups. Prospectively registered on ClinicalTrials.gov (NCT03978416) on June 7, 2019. In this demographically heterogeneous population, language acculturation was generally low, and the frequency of poor dietary behaviors was high. Participants linked financial strain to lower diet quality, as well as anxiety to uncontrolled eating and food cravings. Social support and trust in healthcare professionals were perceived as priorities for healthy eating. Structural and environmental barriers such as affordability and availability of culturally preferred foods were also identified as influences on food choices and eating behavior. This study revealed opportunities for culturally tailored weight management interventions in older Hispanic/Latino adults with obesity. This article is protected by copyright. All rights reserved.
The timing of spring leaf development and fall senescence determine how long deciduous forests actively exchange carbon and water with the atmosphere. Being able to model these dates is therefore critical to accurately representing ecosystem processes in biogeochemical models. Despite this, there has been relatively little effort to improve internal phenology predictions in widely used biogeochemical models. Here, we optimized the phenology algorithms in a regionally developed biogeochemical model (PnET-CN) using phenology data from eight midlatitude PhenoCam sites in eastern North America. We then performed a sensitivity analysis to determine how the optimization affected future predictions of carbon, water, and nitrogen cycling at Bartlett Experimental Forest, New Hampshire. Compared to the original PnET-CN phenology models, our new spring and fall models resulted in shorter season lengths and more abrupt transitions that were more representative of observations. The new phenology models affected daily estimates and interannual variability of modeled carbon exchange, but they did not have a large influence on the magnitude or long-term trends of annual totals. Under future climate projections, our new phenology models predict larger shifts in season length in the fall (1.1 – 3.2 days decade -1 ) compared to the spring (0.9 – 1.5 days decade -1 ). However, for every day the season is longer, our results show that spring can have over twice the effect on annual carbon and water exchange totals compared to the fall. These findings highlight the importance of accurately modeling season length for future projections of carbon and water cycling.
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