Self-formed bedrock waterfalls.

Waterfalls are inspiring landforms that set the pace of landscape evolution as a result of bedrock incision1-3. They communicate changes in sea level or tectonic uplift throughout landscapes2,4 or stall river incision, disconnecting landscapes from downstream perturbations3,5. Here we use a flume experiment with constant water discharge and sediment feed to show that waterfalls can form from a planar, homogeneous bedrock bed in the absence of external perturbations. In our experiment, instabilities between flow hydraulics, sediment transport and bedrock erosion lead to undulating bedforms, which grow to become waterfalls. We propose that it is plausible that the origin of some waterfalls in natural systems can be attributed to this intrinsic formation process and we suggest that investigations to distinguish self-formed from externally forced waterfalls may help to improve the reconstruction of Earth history from landscapes.

More extensive land loss expected on coastal deltas due to rivers jumping course during sea-level rise.

River deltas are home to hundreds of millions of people worldwide and are in danger of sinking due to anthropogenic sea-level rise, land subsidence, and reduced sediment supply. Land loss is commonly forecast by averaging river sediment supply across the entire delta plain to assess whether deposition can keep pace with sea-level rise. However, land loss and deposition vary across the landscape because rivers periodically jump course, rerouting sediment to distinct subregions called delta lobes. Here, we developed a model to forecast land loss that resolves delta lobes and tested the model against a scaled laboratory experiment. Both the model and the experiment show that rivers build land on the active lobe, but the delta incurs gradual land loss on inactive lobes that are cut off from sediment after the river abandons course. The result is a band of terrain along the coast that is usually drowned but is nonetheless a sink for sediment when the lobe is active, leaving less of the total sediment supply available to maintain persistent dry land. Land loss is expected to be more extensive than predicted by classical delta-plain-averaged models. Estimates for eight large deltas worldwide suggest that roughly half of the riverine sediment supply is delivered to terrain that undergoes long periods of submergence. These results draw the sustainability of deltas further into question and provide a framework to plan engineered diversions at a pace that will mitigate land loss in the face of rising sea levels.

Glacial isostatic adjustment directed incision of the Channeled Scabland by Ice Age megafloods.

During the last deglaciation, dozens of glacial outburst floods-among the largest known floods on Earth-scoured the Channeled Scabland landscape of eastern Washington. Over this same period, deformation of the Earth's crust in response to the growth and decay of ice sheets changed the topography by hundreds of meters. Here, we investigated whether glacial isostatic adjustment affected routing of the Missoula floods and incision of the Channeled Scabland from an impounded, glacial Lake Columbia. We used modern topography corrected for glacial isostatic adjustment as an input to flood models that solved the depth-averaged, shallow water equations and compared the results to erosion constraints. Results showed that floods could have traversed and eroded parts of two major tracts of the Channeled Scabland-Telford-Crab Creek and Cheney-Palouse-near 18 ka, whereas glacial isostatic adjustment limited flow into the Cheney-Palouse tract at 15.5 ka. Partitioning of flow between tracts was governed by tilting of the landscape, which affected the filling and overspill of glacial Lake Columbia directly upstream of the tracts. These results highlight the impact of glacial isostatic adjustment on megaflood routing and landscape evolution.

Interviewing young offenders about child-on-child sexual abuse.

This study compared two versions of the NICHD Protocol for interviewing young suspected sexual offenders: the Revised Suspect Protocol (RSP) and the Standard Suspect Protocol (SSP). The RSP incorporated relevant evidence-based practices informed by research on the value of (a) effectively explaining the suspects' rights, (b) rapport building and support, and (c) appropriate questioning strategies. Interviewers using the RSP communicated the children's rights more effectively (reading them more often, checking, verifying, and correcting understanding) and provided more support. In the substantive phase, they remained supportive while recall prompts dominated the questioning. Compared to children in the SSP group, children in the RSP condition understood their rights better, were more responsive during rapport-building, and reacted to interviewer support in the substantive phase with increased responsiveness, which in turn, predicted reduced reluctance, increased emotional expression, and greater informativeness. They were also more likely to make full rather than partial confessions than children in the SSP group. Full confessions were positively predicted by the appropriate communication of legal rights, interviewer support, and reliance on open-ended prompts, thereby confirming the superiority of the RSP relative to the SSP.

Coal fly ash is a major carbon flux in the Chang Jiang (Yangtze River) basin.

Fly ash-the residuum of coal burning-contains a considerable amount of fossilized particulate organic carbon (FOCash) that remains after high-temperature combustion. Fly ash leaks into natural environments and participates in the contemporary carbon cycle, but its reactivity and flux remained poorly understood. We characterized FOCash in the Chang Jiang (Yangtze River) basin, China, and quantified the riverine FOCash fluxes. Using Raman spectral analysis, ramped pyrolysis oxidation, and chemical oxidation, we found that FOCash is highly recalcitrant and unreactive, whereas shale-derived FOC (FOCrock) was much more labile and easily oxidized. By combining mass balance calculations and other estimates of fly ash input to rivers, we estimated that the flux of FOCash carried by the Chang Jiang was 0.21 to 0.42 Mt C⋅y-1 in 2007 to 2008-an amount equivalent to 37 to 72% of the total riverine FOC export. We attributed such high flux to the combination of increasing coal combustion that enhances FOCash production and the massive construction of dams in the basin that reduces the flux of FOCrock eroded from upstream mountainous areas. Using global ash data, a first-order estimate suggests that FOCash makes up to 16% of the present-day global riverine FOC flux to the oceans. This reflects a substantial impact of anthropogenic activities on the fluxes and burial of fossil organic carbon that has been made less reactive than the rocks from which it was derived.

Accelerated river avulsion frequency on lowland deltas due to sea-level rise.

Sea-level rise, subsidence, and reduced fluvial sediment supply are causing river deltas to drown worldwide, affecting ecosystems and billions of people. Abrupt changes in river course, called avulsions, naturally nourish sinking land with sediment; however, they also create catastrophic flood hazards. Existing observations and models conflict on whether the occurrence of avulsions will change due to relative sea-level rise, hampering the ability to forecast delta response to global climate change. Here, we combined theory, numerical modeling, and field observations to develop a mechanistic framework to predict avulsion frequency on deltas with multiple self-formed lobes that scale with backwater hydrodynamics. Results show that avulsion frequency is controlled by the competition between relative sea-level rise and sediment supply that drives lobe progradation. We find that most large deltas are experiencing sufficiently low progradation rates such that relative sea-level rise enhances aggradation rates-accelerating avulsion frequency and associated hazards compared to preindustrial conditions. Some deltas may face even greater risk; if relative sea-level rise significantly outpaces sediment supply, then avulsion frequency is maximized, delta plains drown, and avulsion locations shift inland, posing new hazards to upstream communities. Results indicate that managed deltas can support more frequent engineered avulsions to recover sinking land; however, there is a threshold beyond which coastal land will be lost, and mitigation efforts should shift upstream.

Universal relation with regime transition for sediment transport in fine-grained rivers.

Fine-grained sediment (grain size under 2,000 µm) builds floodplains and deltas, and shapes the coastlines where much of humanity lives. However, a universal, physically based predictor of sediment flux for fine-grained rivers remains to be developed. Herein, a comprehensive sediment load database for fine-grained channels, ranging from small experimental flumes to megarivers, is used to find a predictive algorithm. Two distinct transport regimes emerge, separated by a discontinuous transition for median bed grain size within the very fine sand range (81 to 154 µm), whereby sediment flux decreases by up to 100-fold for coarser sand-bedded rivers compared to river with silt and very fine sand beds. Evidence suggests that the discontinuous change in sediment load originates from a transition of transport mode between mixed suspended bed load transport and suspension-dominated transport. Events that alter bed sediment size near the transition may significantly affect fluviocoastal morphology by drastically changing sediment flux, as shown by data from the Yellow River, China, which, over time, transitioned back and forth 3 times between states of high and low transport efficiency in response to anthropic activities.

Progressive incision of the Channeled Scablands by outburst floods.

The surfaces of Earth and Mars contain large bedrock canyons that were carved by catastrophic outburst floods. Reconstructing the magnitude of these canyon-forming floods is essential for understanding the ways in which floods modify planetary surfaces, the hydrology of early Mars and abrupt changes in climate. Flood discharges are often estimated by assuming that the floods filled the canyons to their brims with water; however, an alternative hypothesis is that canyon morphology adjusts during incision such that bed shear stresses exceed the threshold for erosion by a small amount. Here we show that accounting for erosion thresholds during canyon incision results in near-constant discharges that are five- to ten-fold smaller than full-to-the-brim estimates for Moses Coulee, a canyon in the Channeled Scablands, which was carved during the Pleistocene by the catastrophic Missoula floods in eastern Washington, USA. The predicted discharges are consistent with flow-depth indicators from gravel bars within the canyon. In contrast, under the assumption that floods filled canyons to their brims, a large and monotonic increase in flood discharge is predicted as the canyon was progressively incised, which is at odds with the discharges expected for floods originating from glacial lake outbursts. These findings suggest that flood-carved landscapes in fractured rock might evolve to a threshold state for bedrock erosion, thus implying much lower flood discharges than previously thought.

Low-gradient, single-threaded rivers prior to greening of the continents.

The Silurian-age rise of land plants is hypothesized to have caused a global revolution in the mechanics of rivers. In the absence of vegetation-controlled bank stabilization effects, pre-Silurian rivers are thought to be characterized by shallow, multithreaded flows, and steep river gradients. This hypothesis, however, is at odds with the pancontinental scale of early Neoproterozoic river systems that would have necessitated extraordinarily high mountains if such river gradients were commonplace at continental scale, which is inconsistent with constraints on lithospheric thickness. To reconcile these observations, we generated estimates of paleogradients and morphologies of pre-Silurian rivers using a well-developed quantitative framework based on the formation of river bars and dunes. We combined data from previous work with original field measurements of the scale, texture, and structure of fluvial deposits in Proterozoic-age Torridonian Group, Scotland-a type-example of pancontinental, prevegetation fluvial systems. Results showed that these rivers were low sloping (gradients 10-5 to 10-4), relatively deep (4 to 15 m), and had morphology similar to modern, lowland rivers. Our results provide mechanistic evidence for the abundance of low gradient, single-threaded rivers in the Proterozoic eon, at a time well before the evolution and radiation of land plants-despite the absence of muddy and vegetated floodplains. Single-threaded rivers with stable floodplains appear to have been a persistent feature of our planet despite singular changes in its terrestrial biota.

Digital temperance: adapting an ancient virtue for a technological age.

In technological societies where excessive screen use and internet addiction are becoming constant temptations, the valuable yet intoxicating pleasures of digital technology suggest a need to recover and repurpose temperance, a virtue emphasized by ancient and medieval philosophers. This article reconstructs this virtue for our technological age by reclaiming the most relevant features of Aristotle's and Aquinas's accounts and suggesting five critical revisions needed to adapt the virtue for a contemporary context. The article then draws on this critical interpretation, along with empirical research analyzing the value and dangers of digital technology, to construct a normative account of digital temperance, a virtue that finds a mean between "digital insensibility," the vice of deficiency, and "digital overindulgence," the vice of excess. We conclude by showing how this virtue of digital temperance can help to promote human flourishing in a world saturated with tempting technology.

Impact of River Channel Lateral Migration on Microbial Communities across a Discontinuous Permafrost Floodplain.

Permafrost soils store approximately twice the amount of carbon currently present in Earth's atmosphere and are acutely impacted by climate change due to the polar amplification of increasing global temperature. Many organic-rich permafrost sediments are located on large river floodplains, where river channel migration periodically erodes and redeposits the upper tens of meters of sediment. Channel migration exerts a first-order control on the geographic distribution of permafrost and floodplain stratigraphy and thus may affect microbial habitats. To examine how river channel migration in discontinuous permafrost environments affects microbial community composition, we used amplicon sequencing of the 16S rRNA gene on sediment samples from floodplain cores and exposed riverbanks along the Koyukuk River, a large tributary of the Yukon River in west-central Alaska. Microbial communities are sensitive to permafrost thaw: communities found in deep samples thawed by the river closely resembled near-surface active-layer communities in nonmetric multidimensional scaling analyses but did not resemble floodplain permafrost communities at the same depth. Microbial communities also displayed lower diversity and evenness in permafrost than in both the active layer and permafrost-free point bars recently deposited by river channel migration. Taxonomic assignments based on 16S and quantitative PCR for the methyl coenzyme M reductase functional gene demonstrated that methanogens and methanotrophs are abundant in older permafrost-bearing deposits but not in younger, nonpermafrost point bar deposits. The results suggested that river migration, which regulates the distribution of permafrost, also modulates the distribution of microbes potentially capable of producing and consuming methane on the Koyukuk River floodplain. IMPORTANCE Arctic lowlands contain large quantities of soil organic carbon that is currently sequestered in permafrost. With rising temperatures, permafrost thaw may allow this carbon to be consumed by microbial communities and released to the atmosphere as carbon dioxide or methane. We used gene sequencing to determine the microbial communities present in the floodplain of a river running through discontinuous permafrost. We found that the river's lateral movement across its floodplain influences the occurrence of certain microbial communities-in particular, methane-cycling microbes were present on the older, permafrost-bearing eroding riverbank but absent on the newly deposited river bars. Riverbank sediment had microbial communities more similar to those of the floodplain active-layer samples than permafrost samples from the same depth. Therefore, spatial patterns of river migration influence the distribution of microbial taxa relevant to the warming Arctic climate.

Adoptive Gay Father Families: A Longitudinal Study of Children's Adjustment at Early Adolescence.

Findings are presented from the second phase of a UK longitudinal study of 33 gay father, 35 lesbian mother, and 43 heterosexual parent families when their adopted children reached early adolescence. Participants predominantly lived in urban/suburban areas and were mostly white and well-educated. Standardized interviews, observations, and questionnaires of parental mental health, parent-child relationships, and adolescent adjustment were administered to parents, children, and teachers between 2016 and 2018. There were few differences between family types. However, adjustment problems had increased in all family types, with better parenting quality and parental mental health associated with fewer adjustment problems. The findings contribute to adoption policy and practice, and to theoretical understanding of the role of parental gender in child development.

The dynamics of two-session interviews with suspected victims of abuse who are reluctant to make allegations.

Supportive forensic interviews conducted in accordance with the National Institute of Child Health and Human Development Revised Protocol (RP) help many alleged victims describe abusive experiences. When children remain reluctant to make allegations, the RP guides interviewers to (a) focus on rapport building and nonsuggestive support in a first interview, and (b) plan a second interview to allow continued rapport building before exploring for possible abuse. We explored the dynamics of such two-session RP interviews. Of 204 children who remained reluctant in an initial interview, we focused on 104 who made allegations when re-interviewed a few days later. A structural equation model revealed that interviewer support during the first session predicted children's cooperation during the rapport-building phase of the second session, which, in turn, predicted more spontaneous allegations, which were associated with the interviewers' enhanced use of open-ended questions. Together, these factors mediated the effects of support on children's free recall of forensically important information. This highlighted the importance of emphasizing rapport with reluctant children, confirming that some children may need more time to build rapport even with supportive interviewers.

Infants' stress responses and protest behaviors at childcare entry and the role of care providers.

During the transition from home to childcare, 70 15-month-old infants were videotaped, and their negative emotions were rated. Infants' attachments to mothers were assessed prior to child care entry and to care providers five months later using the Strange Situation Procedure (SSP). Infant heart rate was monitored at home, during adaptation to childcare (mothers present), and during subsequent separations. Respiratory sinus arrhythmia (RSA) was computed from the beat-to-beat measures of heart rate to reflect vagal tone, which is reduced during chronic states of stress, and was collected upon Arrival, during in-group Play, and when in the Group more generally. All infants responded to childcare entry with low RSA levels indicating stress. However, during adaptation with the mother present, RSA was higher for securely attached infants. On the first separation day, 35.3% of the infants fussed and cried extensively. These intense protests predicted later secure attachments to care providers, which adaptively helped to reduce stress, especially in infants who protested extensively, as if summoning their mothers back. Because extensive protest suggests limited regulatory capacities, infants risk overburdening the stress system when left unsupported.

Linguistically complex recognition prompts in pre-recorded cross-examinations.

This study examined the effects of pre-trial preparation and pre-recorded cross-examinations on the linguistic complexity of recognition prompts (i.e., option-posing or suggestive questions) used when questioning child victims in English criminal courts. The study also compared the linguistic complexity of recognition prompts that did and did not contain suggestive content. Analyses compared 43 cases that involved pre-recorded cross-examinations with pre-trial preparation and 44 cases that did not, which occurred between 2012 and 2016. Cases utilizing the "special measures" contained fewer linguistically complex prompts with and without suggestive content than did their counterparts, demonstrating the benefits of those special measures. Overall, linguistically complex recognition prompts were more likely to contain suggestive content than other recognition prompts. However, linguistically complex prompts with and without suggestive content were still frequently used despite the special measures, demonstrating the need for further professional training to improve the quality of children's evidence.

Development of an Interactive Remote Basic Surgical Skills Mini-Curriculum for Medical Students During the COVID-19 Pandemic.

Introduction. Teaching surgical skills has historically been a hands-on activity, with instructors and learners in close physical proximity. This paradigm was disrupted by the COVID-19 pandemic, requiring innovative solutions to surmount the challenges of teaching surgical skills remotely. In this work, we describe our institution's path and early results of developing an interactive remote surgical skills course for medical students in the surgical clerkship. Methods. 31 third-year medical students were distributed a set of surgical equipment and 3D printed phone dock. Each participant completed a baseline questionnaire and underwent 3 structured interactive remote sessions on surgical instruments, knot tying, and suturing techniques. Students were instructed on sharing their first-person viewpoint and received real-time feedback on their knot tying and suturing techniques from the course instructor. Pre- and post-session surveys were conducted and analyzed. Results. All students were able to complete the remote surgical skills course successfully, as defined by visually demonstrating successful two-handed knot and simple suture techniques. Students' aggregate confidence score in their knot tying ability (pretest mean 7.9, SD 0.7 vs posttest mean 9.7, SD 0.9, t-statistic -2.3, P = .03) and suturing ability (pretest mean 8.0, SD 1.3 vs posttest mean 13.8, SD 0.9 t-statistic -5.5, P < .001) significantly improved after the intervention. Qualitative feedback from the students underscored the utility of the first-person perspective for teaching surgical technique. Conclusion. This study demonstrates that remote teaching of knot tying and simple suturing to medical students can be effectively implemented using a remote learning curriculum that was well received by the learners.

Gender-Typed and Gender-Segregated Play Among Tanzanian Hadza and Congolese BaYaka Hunter-Gatherer Children and Adolescents.

Few data exist on gender-typed and gender-segregated play in hunter-gatherer societies, despite their unique demographic and cultural features which may influence children's gendered play. Using naturalistic observations of Hadza (N = 46, 41% female) and BaYaka (N = 65, 48% female) hunter-gatherer 3- to 18-year-olds from Tanzania and the Republic of Congo, we showed that access to playmates was negatively associated with playing in mixed-gender groups. Young boys did not engage in more rough-and-tumble play than girls, but adolescent boys participated in this type of play more than adolescent girls. Children were also more likely to participate in work-themed play which conformed to gender norms within their society. Findings are discussed within the context of gendered division of labor, child autonomy, and demography.

Father-child attachment in adoptive gay father families.

The attachment security of children in 30 gay father families, 29 lesbian mother families and 38 heterosexual parent families was investigated using the Friends and Family Interview (FFI) at the second phase of a longitudinal study. Children in gay father families showed significantly higher levels of secure-autonomous attachment than children in heterosexual parent families, significantly lower levels of preoccupied attachment than children in either lesbian mother or heterosexual parent families, and significantly lower levels of disorganised attachment than children in heterosexual parent families. For children in gay father families, stepwise multiple regression revealed that neither hyperactivity nor emotional symptoms at Phase 1 were predictive of disorganisation at Phase 2. However, when entered alone, Phase 1 emotional symptoms predicted Phase 2 disorganisation. The results indicate that adopted children in gay father families are at least as likely to be securely attached as children in lesbian mother or heterosexual parent families.

Is interviewer support associated with the reduced reluctance and enhanced informativeness of alleged child abuse victims?

Child maltreatment victims are often reluctant to report abuse when formally interviewed. Evidence-based guidelines like the National Institute of Child Health and Human Development Standard Investigative Interview Protocol do not adequately address such reluctance because they are focused on cognitive rather than socioemotional strategies. The present study was designed to determine whether the Revised National Institute of Child Health and Human Development Protocol, which emphasizes supportive interviewing more than the standard protocol does, might predict increases in the overall informativeness and reductions in the reluctance of alleged victims. A total of 254 interviews, 166 using the revised protocol and 88 using the standard protocol, were conducted with 4.06- to 13.98-year-old children (M = 9.20, SD = 2.49) who disclosed multiple incidents of physical abuse by their parents and were thus expected to be more reluctant than victims of extrafamilial abuse. We coded indices of interviewer support and question types, children's reluctance, and informativeness in each utterance during the substantive phases of the interviews. The Revised Protocol was associated with better interviewer support and questioning as well as reduced reluctance and increased informativeness on the part of the children. These findings document the value of training interviewers to attend to the socioemotional needs of suspected abuse victims during investigative interviews. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Geographically varying associations between personality and life satisfaction in the London metropolitan area.

Residential location is thought to influence people's well-being, but different individuals may value residential areas differently. We examined how life satisfaction and personality traits are geographically distributed within the UK London metropolitan area, and how the strength of associations between personality traits and life satisfaction vary by residential location (i.e., personality-neighborhood interactions). Residential area was recorded at the level of postal districts (216 districts, n = 56,019 participants). Results indicated that the strength of associations between personality traits and life satisfaction depended on neighborhood characteristics. Higher openness to experience was more positively associated with life satisfaction in postal districts characterized by higher average openness to experience, population density, and ethnic diversity. Higher agreeableness and conscientiousness were more strongly associated with life satisfaction in postal districts with lower overall levels of life satisfaction. The associations of extraversion and emotional stability were not modified by neighborhood characteristics. These findings suggest that people's life satisfaction depends, in part, on the interaction between individual personality and particular features of the places they live.