ALBERT

Description: 〈div data-abstract-type="normal"〉〈p〉Although the thermal evolution of the mantle before c. 3.0 Ga remains unclear, since c. 3.0 Ga secular cooling has dominated over heat production—this is time's arrow. By contrast, the thermal history of the crust, which is preserved in the record of metamorphism, is more complex. Heat to drive metamorphism is generated by radioactive decay and viscous dissipation, and is augmented by the influx of heat from the mantle. Notwithstanding that reliable data are sparse before the Neoarchean, we use a dataset of temperature (〈span〉T〈/span〉), pressure (〈span〉P〈/span〉) and thermobaric ratio (〈span〉T〈/span〉/〈span〉P〈/span〉 at the metamorphic ‘peak’), and age of metamorphism (〈span〉t〈/span〉, the timing of the metamorphic ‘peak’) for rocks from 564 localities ranging in age from the Cenozoic to the Eoarchean eras to interrogate the crustal record of metamorphism as a proxy for the heat budget of the crust through time. On the basis of 〈span〉T〈/span〉/〈span〉P〈/span〉, metamorphic rocks are classified into three natural groups: high T/P type (〈span〉T/P〈/span〉 〉775°C/GPa, mean 〈span〉T/P〈/span〉 ~1105°C/GPa), including common and ultrahigh-temperature granulites, intermediate T/P type (〈span〉T/P〈/span〉 between 775 and 375°C/GPa, mean 〈span〉T/P〈/span〉 ~575°C/GPa), including high-pressure granulites and medium- and high-temperature eclogites, and low T/P type (〈span〉T/P〈/span〉 T/P ~255°C/GPa), including blueschists, low-temperature eclogites and ultrahigh-pressure metamorphic rocks. A monotonic increase in the 〈span〉P〈/span〉 of intermediate T/P metamorphism from the Neoarchean to the Neoproterozoic reflects strengthening of the lithosphere during secular cooling of the mantle—this is also time's arrow. However, temporal variation in the 〈span〉P〈/span〉 of intermediate T/P metamorphism and in the moving means of 〈span〉T〈/span〉 and 〈span〉T〈/span〉/〈span〉P〈/span〉 of high T/P metamorphism, combined with the clustered age distribution, demonstrate the cyclicity of collisional orogenesis and cyclic variations in the heat budget of the crust superimposed on secular cooling since c. 3.0 Ga—this is time's cycle. A first cycle began with the widespread appearance/survival of intermediate T/P and high T/P metamorphism in the Neoarchean rock record coeval with amalgamation of dispersed blocks of lithosphere to form protocontinents. This cycle was terminated by the fragmentation of the protocontinents into cratons in the early Paleoproterozoic, which signalled the start of a new cycle. The second cycle continued with the progressive amalgamation of the cratons into the supercontinent Columbia and extended until the breakup of the supercontinent Rodinia in the Neoproterozoic. This cycle represented a period of relative tectonic and environmental stability, and perhaps reduced subduction during at least part of the cycle. During most of the Proterozoic the moving means for both 〈span〉T〈/span〉 and 〈span〉T〈/span〉/〈span〉P〈/span〉 of high T/P metamorphism exceeded the arithmetic means, reflecting insulation of the mantle beneath the quasi-integrated lithosphere of Columbia and, after a limited reorganisation, Rodinia. The third cycle began with the steep decline in thermobaric ratios of high T/P metamorphism to their lowest value, synchronous with the breakup of Rodinia and the formation of Pannotia, and the widespread appearance/preservation of low T/P metamorphism in the rock record. The thermobaric ratios for high T/P metamorphism rise to another peak associated with the Pan-African event, again reflecting insulation of the mantle. The subsequent steep decline in thermobaric ratios of high T/P metamorphism associated with the breakup of Pangea at c. 0.175 Ga may indicate the start of a fourth cycle. The limited occurrence of high and intermediate T/P metamorphism before the Neoarchean suggests either that suitable tectonic environments to generate these types of metamorphism were not widely available before then or that the rate of survival was low. We interpret the first cycle to record stabilisation of subduction and the emergence of a network of plate boundaries in a plate tectonics regime once the balance between heat production and heat loss changed in favour of secular cooling, possibly as early as c. 3.0 Ga in some areas. This is inferred to have been a globally linked system by the early Paleoproterozoic, but whether it remained continuous to the present is unclear. The second cycle was characterised by stability from the formation of Columbia to the breakup of Rodinia, generating higher than average 〈span〉T〈/span〉 and 〈span〉T〈/span〉/〈span〉P〈/span〉 of high T/P metamorphism. The third cycle reflects colder collisional orogenesis and deep subduction of the continental crust, features that are characteristic of modern plate tectonics, which became possible once the average temperature of the asthenospheric mantle had declined to 〈/p〉〈/div〉

Description: Abstract The megaregolith of the Moon is the upper region of the crust, which has been extensively fractured by intense impact bombardment. Little is known about the formation and evolution of the lunar megaregolith. Here, we implement the Grady‐Kipp model for dynamic fragmentation into the iSALE shock physics code. This implementation allows us to directly simulate tensile in situ impact fragmentation of the lunar crust. We find that fragment sizes are weakly dependent on impactor size and impact velocity. For impactors 1 km in diameter or smaller, a hemispherical zone centered on the point of impact contains meter scale fragments. For an impactor 1 km in diameter this zone extends to depths of 20 km. At larger impactor sizes, overburden pressure inhibits fragmentation and only a near surface zone is fragmented. For a 10 km diameter impactor, this surface zone extends to a depth of ~20 km and lateral distances ~300 km from the point of impact. This suggests that impactors from 1‐10 km in diameter can efficiently fragment the entire lunar crust to depths of ~20 km, implying that much of the modern day megaregolith can be created by single impacts rather than by multiple large impact events.

Description: Since at least T. H. Marshall, scholars have recognized military service as a form of sacrifice that warrants compensation from the state. War-widow pensions, expansion of the franchise, and subsidized higher education are all examples of rights and benefits “bestowed” in return for wartime mobilization. Similarly, in the United States, governments have hired veterans preferentially for civilian public jobs as recompense for active military service. Although oft overlooked, those policies seem influential: the percentage of job holders identifying as veterans in the civilian US executive branch exceeds the proportion in the wider population by several multiples. This century-old pattern suggests another way that wartime mobilization has influenced the state. Yet, efforts to understand it have struggled to rule out the possibility that those who serve in the armed forces are predisposed to work for the state in both military and civilian capacities. Here, we rule out this possibility by examining whether birthdates randomly called for induction in the Vietnam-Era Selective Service Lotteries (VSSL) appear disproportionately in the population of nonsensitive personnel records of the civilian US executive branch. We find that birthdates called for induction appear with unusually high frequency among employees who were draft eligible and at risk for induction but not among other employees. This finding suggests a treatment effect from military service, thus dovetailing with the hypothesis that wartime mobilization has substantially and continually influenced who works in the contemporary administrative state.

Description: Recently it was shown that individual differences in attention style in infants are associated with childhood effortful control, surgency, and hyperactivity-inattention. Here we investigated whether effortful control, surgency and behavioral problems in childhood can be predicted even earlier, from individual differences in newborns’ average duration of gaze to stimuli. Eighty newborns participated in visual preference and habituation studies. Parents completed questionnaires at follow up (mean age = 7.5 years, SD = 1.0 year). Newborns’ average dwell time was negatively associated with childhood surgency (β = −.25, R2 = .04, p = .02) and total behavioral difficulties (β = −.28, R2 = .05, p = .04) but not with effortful control (β = .03, R2 = .001, p = .76). Individual differences in newborn visual attention significantly associated with individual variation in childhood surgency and behavioral problems, showing that some of the factors responsible for this variation are present at birth. Scientific Reports 5 doi: 10.1038/srep11264

Description: Conserving migratory birds is made especially difficult because of movement among spatially disparate locations across the annual cycle. In light of challenges presented by the scale and ecology of migratory birds, successful conservation requires integrating objectives, management, and monitoring across scales, from local management units to ecoregional and flyway administrative boundaries. We present an integrated approach using a spatially explicit energetic-based mechanistic bird migration model useful to conservation decision-making across disparate scales and locations. This model moves a mallard-like bird ( Anas platyrhynchos ), through spring and fall migration as a function of caloric gains and losses across a continental-scale energy landscape. We predicted with this model that fall migration, where birds moved from breeding to wintering habitat, took a mean of 27.5 days of flight with a mean seasonal survivorship of 90.5% (95% CI = 89.2%, 91.9%) whereas spring migration took a mean of 23.5 days of flight with mean seasonal survivorship of 93.6% (95% CI = 92.5%, 94.7%). Sensitivity analyses suggested that survival during migration was sensitive to flight speed, flight cost, the amount of energy the animal could carry and the spatial pattern of energy availability, but generally insensitive to total energy availability per se . Nevertheless, continental patterns in the bird-use days occurred principally in relation to wetland cover and agricultural habitat in the fall. Bird-use days were highest in both spring and fall in the Mississippi Alluvial Valley and along the coast and near-shore environments of South Carolina. Spatial sensitivity analyses suggested that locations nearer to migratory endpoints were less important to survivorship; for instance, removing energy from a 1,036 km 2 stopover site at a time from the Atlantic Flyway suggested coastal areas between New Jersey and North Carolina, including Chesapeake Bay and the North Carolina piedmont, are essential locations for efficient migration and increasing survivorship during spring migration but not locations in Ontario and Massachusetts. This sort of spatially explicit information may allow decision-makers to prioritize their conservation actions toward locations most influential to migratory success. Thus, this mechanistic model of avian migration provides a decision-analytic medium integrating the potential consequences of local actions to flyway-scale phenomena. This article is protected by copyright. All rights reserved.

Description: Because of the non‐stationary character of the North Atlantic atmospheric flow on time‐scales of several decades, short hindcast periods are not sufficiently representative for the longer‐term behaviour of the climate system, and small sample sizes can lead to skill estimates, in particular of correlation, that are not robust. Our findings provide a simple but plausible explanation for the apparently conflicting findings of under‐ and overconfidence over parts of the North Atlantic. Atmospheric seasonal predictability in winter over the Euro‐Atlantic region is studied with an emphasis on the signal‐to‐noise paradox of the North Atlantic Oscillation. Seasonal hindcasts of the ECMWF model for the recent period 1981–2009 show, in agreement with other studies, that correlation skill over Greenland and parts of the Arctic is higher than the signal‐to‐noise ratio implies. This leads to the paradoxical situation where the real world appears more predictable than the models suggest, with the forecast ensembles being overly dispersive (or underconfident). However, it is demonstrated that these conclusions are not supported by the diagnosed relationship between ensemble mean root‐mean‐square error (RMSE) and ensemble spread which indicates a slight under‐dispersion (overconfidence). Furthermore, long atmospheric seasonal hindcasts suggest that over the 110‐year period from 1900 to 2009 the ensemble system is well calibrated (neither over‐ nor under‐dispersive). The observed skill changed drastically in the middle of the twentieth century and paradoxical regions during more recent hindcast periods were strongly under‐dispersive during mid‐century decades. Due to non‐stationarities of the climate system in the form of decadal variability, relatively short hindcasts are not sufficiently representative of longer‐term behaviour. In addition, small hindcast sample size can lead to skill estimates, in particular of correlation measures, that are not robust. It is shown that the relative uncertainty due to small hindcast sample size is often larger for correlation‐based than for RMSE‐based diagnostics. Correlation‐based measures like the RPC are shown to be highly sensitive to the strength of the predictable signal, implying that disentangling of physical deficiencies in the models on the one hand, and the effects of sampling uncertainty on the other hand, is difficult. Given the current lack of a causal physical mechanism to unravel the puzzle, our hypotheses of non‐stationarity and sampling uncertainty provide simple yet plausible explanations for the paradox.