When dynamic soil-structure interaction (DSSI) analyses are performed, e.g. using the finite element (FE) method, the input signal is required at the base of the model. Nevertheless, acceleration ...records are usually available at the surface and, therefore, the desired motion must be deconvolved to the base. The latter is usually performed through the solution of one-dimensional propagation of shear waves in an elastic medium, in the frequency domain. Herein, nonlinear behavior is generally incorporated through the equivalent-linear method, by iteratively reducing the stiffness and increasing the critical damping ratio as a function of the maximum strains attained in each iteration. However, if complex material models are adopted to characterize the soil, the input motion derived with the equivalent linear method will not be compatible due to the simplified approach used to represent the nonlinear behavior. In this article, the use of a procedure to perform a time-domain deconvolution in non-linear elastoplastic materials is demonstrated. The goal is to generate input accelerograms at the base of a FE model to perform DSSI analyses. The procedure is based on the iterative modification of the motion at the base according to the relative differences between the propagated and target surface spectra. To illustrate the use of the methodology, it was applied to a FE model of the Treasure Island site (San Francisco, US), to derive the required motion at the base from a record of the Loma Prieta earthquake.•This article provides a useful guideline to optimize the use of the deconvolution procedure to derive input motions for dynamic FE analyses considering nonlinear elastoplastic materials.
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Lay Summary Individuals with different personalities may also differ in how they make decisions. We tested stickleback fish in a maze task and expected that bolder fish would make quicker but less ...accurate decisions. In fact, we found different personalities to be equally good at the task. This might explain why we often find bold leaders in fish shoals as they make both quick and accurate decisions.There have been many investigations into consistent, individual differences in behavior (animal personalities), but rather less attention has been given to the possibility that individuals might differ consistently in their "cognitive style," which refers to the way information is acquired, processed, stored, or acted on. Both personality and cognition have important fitness consequences, and it has been proposed that variation in cognition could be functionally related to variation in personality. Here, we test this hypothesis using three-spined sticklebacks (Gasterosteus aculeatus) as a model and adopt a classic T-maze with food reward experimental paradigm. We first confirmed that fish choose the correct arm of the maze significantly more than would be expected by chance and that this improves with trial number. We then explored predictors of individual differences in the speed (time to making a decision) and accuracy (whether the first decision is correct) in decision making. We find bolder behavioral types (who tend to be male) arrive at the correct decision sooner than their shyer conspecifics. However, boldness was not related to decision accuracy. Moreover, we did not find any significant difference in fish's improvement in decision accuracy over successive trials according to boldness or sex. This suggests that although bolder fish may acquire information more quickly because they make decisions faster, they do not differ from shyer conspecifics in their decision-making accuracy. The absence of such a trade-off might offer a functional explanation for why, in stickleback fish and many other species, bolder individuals tend to initiate movement and shyer individuals to follow-bold leaders may result in faster group decisions without compromising accuracy.
Material damping in a stratified soil deposit Díaz, Miguel A.; Mánica, Miguel A.; Botero, Eduardo ...
Earth sciences research journal,
02/2023, Volume:
26, Issue:
4
Journal Article
Peer reviewed
Due to the extensive use of one-dimensional equivalent linear analyses to determine the free-field response of nonlinear soil deposits, dynamic numerical simulations able to reproduce an analogous ...response to equivalent linear codes are of great value for practical engineering, particularly for dynamic soil-structure interaction problems. An appealing alternative, for problems not close to a failure condition, is to assume a linear elastic behaviour of the soil but with stiffness parameters derived from one-dimensional equivalent linear analyses, i.e. consistent with the level of deformation induced by the input motion. In this approach, energy dissipation has to be artificially incorporated through material damping formulations. In this work, local, Rayleigh, and hysteretic damping formulations in FLAC were assessed to emulate results from one-dimensional equivalent linear analysis. A main feature of the analyses is that they consider a site having a considerably stratified soil deposit, in which the shear wave velocity profile displays significant variations and where the selection of some parameters in the damping formulations is not a trivial task. Results provide relevant insights into the performance of the adopted damping formulations and the selection of material damping parameters to reproduce results of equivalent linear analyses.
A genomic history of Aboriginal Australia Malaspinas, Anna-Sapfo; Westaway, Michael C; Muller, Craig ...
Nature (London),
10/2016, Volume:
538, Issue:
7624
Journal Article
Peer reviewed
Open access
The population history of Aboriginal Australians remains largely uncharacterized. Here we generate high-coverage genomes for 83 Aboriginal Australians (speakers of Pama-Nyungan languages) and 25 ...Papuans from the New Guinea Highlands. We find that Papuan and Aboriginal Australian ancestors diversified 25-40 thousand years ago (kya), suggesting pre-Holocene population structure in the ancient continent of Sahul (Australia, New Guinea and Tasmania). However, all of the studied Aboriginal Australians descend from a single founding population that differentiated ~10-32 kya. We infer a population expansion in northeast Australia during the Holocene epoch (past 10,000 years) associated with limited gene flow from this region to the rest of Australia, consistent with the spread of the Pama-Nyungan languages. We estimate that Aboriginal Australians and Papuans diverged from Eurasians 51-72 kya, following a single out-of-Africa dispersal, and subsequently admixed with archaic populations. Finally, we report evidence of selection in Aboriginal Australians potentially associated with living in the desert.
In this paper, the correlation between different seismic intensity measures (IM) and engineering demand parameters (EDP) of reinforced concrete (RC) buildings was evaluated by means of nonlinear ...dynamic analyses (NLDA). The Costa Rican ground motion database and four RC buildings (4-, 6-, 8- and 10-stories) were considered in this research. Estimations of conventional IMs were derived directly from the ground motion records as well as from the response of a single degree of freedom (SDOF) linear oscillator, with a period equal to that of the fundamental period of the buildings. NLDAs were performed using unscaled and scaled records to account for different intensity levels, and the performance of the buildings was characterized in terms of three EDPs: the average inter-story drift ratio, the maximum inter-story drift ratio, and the Park & Ang damage index. Results demonstrate a significant improvement in the correlation between IMs and EDPs when the dynamic characteristics of the structure are accounted for through the response of the SDOF oscillator. On the other hand, the peak ground velocity turned out to be an effective IM, independent of the dynamic characteristics of the buildings. This is very useful when assessing potential seismic damage both for immediate decision-making and for the characterization of the seismic hazard of a region.
When individuals invest in a common good, an efficient outcome is hard to achieve, because each can free ride on others' efforts. This problem can lead parents that raise their young together to ...reduce their investment in care, with negative consequences for offspring. Here, we present a mathematical model to show that a strategy of conditional cooperation, in which parents take turns feeding their young, can help to resolve this problem. To test this idea, we studied the behavior of great tit parents raising chicks together. We found that parents alternated visits to the nest more than would be expected by chance, speeding up their feeding rate after their partner had visited the chicks, but slowing down again once they had visited in turn. This effect was not mediated by visit-to-visit changes in offspring begging intensity, although females (but not males) were influenced by mean begging levels across broods. We conclude that conflict over parental investment in this species is partly ameliorated by a simple form of reciprocity.
Global human genetic variation is greatly influenced by geography, with genetic differentiation between populations increasing with geographic distance and within-population diversity decreasing with ...distance from Africa. In fact, these ’clines’ can explain most of the variation in human populations. Despite this, population genetics inferences often rely on models that do not take geography into account, which could result in misleading conclusions when working at global geographic scales. Geographically explicit approaches have great potential for the study of human population genetics. Here, we discuss the most promising avenues of research in the context of human settlement history and the detection of genomic elements under natural selection. We also review recent technical advances and address the challenges of integrating geography and genetics.
Infection with the hepatitis B virus (HBV) leads to different disease outcomes, which can be broadly divided into three categories: acute mild infection, 'fulminant' and chronic hepatitis (long-term ...persistent form of the infection). The factors that influence the development of these different disease states are poorly understood and may include viral polymorphisms. To investigate this possibility, we analysed 116 published complete HBV genomes for which we knew disease outcome and had access to associated information on patients (age, sex and geographic origin). Our best statistical model correctly classified 72% of the cases and retained age and sex of the patient, as well as 29 candidate mutations. With the exception of one mutation in the X gene, all were located in the viral polymerase, suggesting this gene plays a critical role in clinical outcome. Our results highlight the importance of the genetics of HBV strains in the evolution of the disease and demonstrate that disease outcome can be predicted to a surprisingly large extent with a limited number of host and viral factors.
The South Pacific Gyre is the world’s largest expanse of oligotrophic ocean and supports communities of endemic gadfly petrels Pterodroma spp., yet little is known about their foraging ecology in ...this nutrient-poor environment. We tracked Murphy’s petrels Pterodroma ultima with geolocators from Henderson Island, Pitcairn Islands, for 2 consecutive years (2011 to 2013). During pre-laying exodus, petrels travelled south and southwest of the colony, with males travelling further than females to more productive waters. During incubation, birds foraged at the southern and eastern edges of the Gyre, with some travelling over 4800 km from the colony, the greatest recorded foraging range of any breeding seabird. During non-breeding, the petrels migrated to the Subarctic Gyre in the North Pacific to forage in cool, mesotrophic waters. Habitat models revealed that these birds do not have clear preferences for oceanographic (such as fronts or eddies) or topographic (seamounts) features, generally favouring deep and unproductive waters. Analyses of activity patterns indicated Murphy’s petrels are amongst the most active of all seabirds, particularly during incubation when they spent ca. 95% of their time at sea in flight. The birds did not appear to forage during darkness, but flight activity peaked at dawn, particularly during non-breeding, suggesting they feed on mesopelagic prey that are diel vertical migrants. At-sea protection for such a wide-ranging species would require management at huge spatial scales, and hence in the short term, the principal focus for conservation should be on eliminating the immediate threat from invasive mammals at breeding sites.
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