Extinction Processes Research Articles

Toxic mercury pulses into late Permian terrestrial and marine environments

Abstract Large spikes in mercury (Hg) concentration are observed globally at the latest Permian extinction (LPE) horizon that are thought to be related to enhanced volcanic emissions of the Siberian Traps large igneous province (LIP). While forming an effective chemostratigraphic marker, it remains unclear whether such enhanced volcanic Hg emissions could have generated toxic conditions that contributed to extinction processes. To address this, we examined the nature of enhanced Hg emissions from the Siberian Traps LIP and the potential impact it may have had on global ecosystems during the LPE. Model results for a LIP eruption predict that pulses of Hg emissions to the atmosphere would have been orders of magnitude greater than normal background conditions. When deposited into world environments, this would have generated a series of toxic shocks, each lasting >1000 yr. Such repeated Hg loading events would have had severe impact across marine trophic levels, as well as been toxic to terrestrial plant and animal life. Such high Hg loading rates may help explain the co-occurrence of marine and terrestrial extinctions.

Millennial-scale ocean redox and δ13C changes across the Permian–Triassic transition at Meishan and implications for the biocrisis

The Permian–Triassic extinction was the largest Phanerozoic mass extinction event, yet its ultimate causes remain unresolved. Ocean redox conditions, global warming, and carbon cycle perturbations owing to massive volcanism and their inter-relationships are keys to resolve the origins of this event. We here assess such relationships using a method to obtain an instantaneous stratigraphic response from high-resolution (millennial-scale) records of carbonate-δ13C and pyrite framboid size distributions across the Permian–Triassic boundary (PTB) at Meishan, China. We report two gradual long-term negative δ13C shifts before and after the PTB. Late Permian ocean redox conditions varied through three successive oxic–dysoxic, dysoxic–euxinic, and high-frequency euxinic stages. Oxic and high-frequency euxinic events occurred in the early Griesbachian and middle Griesbachian, respectively. The short-term euxinia events were not associated with the negative δ13C excursions. Siberian volcanism could have produced large light-carbon inputs, global warming, and low-oxygen conditions at intermediate ocean depths, but it may not directly drive high-frequency euxinia across the PTB. Long-term dysoxia and occasional euxinia well before the PTB stressed mobile macroorganisms and caused gradual extinction before the major extinction event. High-frequency latest Permian euxinia reduced overall biotic adaptability, and caused the initial rapid mass extinction. Increasing temperatures and other deleterious environment factors then reinforced the extinction process. Oxic conditions contributed to biotic recovery immediately after the mass extinction in the early Griesbachian. Further millennial-scale dysoxic/euxinic alternations in the middle Griesbachian would have prolonged Early Triassic biotic recovery.

“But what silence! No more gazelles…”: Occurrence and extinction of fauna in Lesotho, southern Africa, since the late Pleistocene

Understanding the historical dynamics of wildlife distribution and abundance is essential to developing appropriate conservation measures. Here we investigate the occurrence and status of medium-to large-sized fauna (excluding avifauna) for the mountain Kingdom of Lesotho and immediate adjoining regions of South Africa, from the late Pleistocene to the present-day. We provide historical timelines and records of reported medium to large faunal taxa based on: data from eight published archaeological excavations, analyses of several hundred unpublished 19th and 20th century historical documents (including missionary letters, diaries, colonial reports and newspapers), and 58 recent oral history interviews. Vegetation and climate changes through the Holocene are also noted, based on archaeo-botanical records. Through these sources, we record 61 medium to large faunal species for Lesotho and surrounding regions over the past ~21 ka, of which only 22 are present today. Some species not previously known to the region are documented (e.g. Temminck's pangolin). Most species were present during the early 19th century, but many regional species extinctions and a major faunal population decline occurred between 1845 and 1850, owing mainly to settler hunting campaigns. Subsequent extinctions have taken place over a wider temporal interval, due to factors including overhunting, human-wildlife conflicts and habitat loss. It seems that some taxa were forced into unsuitable mountain refugia where species eventually succumbed to genetic erosion and/or harsh climatic conditions. Our results increase current understanding of regional faunal and environmental changes, such as the timing of species occurrences and extinction events and processes in Lesotho. Such work adds valuable knowledge to understanding the environmental heritage of the region. Information can be disseminated into wildlife records, national environmental reports, the WWF, the national school environmental educational curriculum and to National Parks and Heritage Sites.

A Likelihood Framework for Modeling Pairwise Beta Diversity Patterns Based on the Tradeoff Between Colonization and Extinction

Ecological communities are assembled by various mechanisms, including a tradeoff between colonization and extinction processes. However, it is still unclear how this tradeoff influences pairwise beta diversity pattern. Herein, we propose a novel likelihood framework to disentangle the compound impacts of species’ colonization and extinction rates on community-level compositional dissimilarity which are ignored by traditional indices. The framework infers two parameters of colonization and extinction rates, allowing ecologists to study their latitudinal or broad-scale spatial variation patterns and test the relative influences of associated environmental factors. More importantly, the likelihood-based model showed that multi-site beta diversity is essentially identical to the local colonization failure or extinction rate of species in newly colonized sites, but is not related to species’ colonization rates. Profoundly, the present likelihood model allows ecologists to explicitly infer the independent species’ colonization rate parameter and test its underpinning mechanisms, as it can be proven that this parameter would be only implicitly measured if used to compute multi-site beta diversity indices. KEYWORDS: beta diversity, island biogeography theory, ecological mechanisms, community assembly, biodiversity survey

Landscapes of Extraction and the Memories of Extinction in Patricio Guzmán’s Nostalgia de la luz and El botón de nácar

Focusing on Guzmán's essay films Nostalgia de la luz (2010) and El botón de nácar (2015), in this article I argue that the ambiguity between reference and abstraction that pervades the visual representation of landscape in late capitalism offers a productive way to map out the processes of extinction caused by continual histories of extraction. This ambiguity not only reveals the limits of the landscape-form to convey the degradation of nature, but also the progressive disappearance of the human subject from the center of history in such spaces where capital seeks time and time again to resolve its internal contradictions through new forms of resource extraction. In this fashion, Guzmán’s totalizing aspiration to represent the historical, archaeological, and even cosmological pasts through the landscapes of the Atacama Desert and Patagonia becomes a way to explain how capital has moved from the human to the planetary, which entails a larger alteration of ecological metabolism and transforms extinction into the only historical horizon. I conclude that the memory of past processes of extraction and extinction inscribed in these landscapes can also function as a prolepsis of a future without us, thus presenting an opportunity to reactivate the subject’s historical potential to change the way we relate to nature.

Dysregulation of inflammation, neurobiology, and cognitive function in PTSD: an integrative review.

Compelling evidence from animal and human research suggest a strong link between inflammation and posttraumatic stress disorder (PTSD). Furthermore, recent findings support compromised neurocognitive function as a key feature of PTSD, particularly with deficits in attention and processing speed, executive function, and memory. These cognitive domains are supported by brain structures and neural pathways that are disrupted in PTSD and which are implicated in fear learning and extinction processes. The disruption of these supporting structures potentially results from their interaction with inflammation. Thus, the converging evidence supports a model of inflammatory dysregulation and cognitive dysfunction as combined mechanisms underpinning PTSD symptomatology. In this review, we summarize evidence of dysregulated inflammation in PTSD and further explore how the neurobiological underpinnings of PTSD, in the context of fear learning and extinction acquisition and recall, may interact with inflammation. We then present evidence for cognitive dysfunction in PTSD, highlighting findings from human work. Potential therapeutic approaches utilizing novel pharmacological and behavioral interventions that target inflammation and cognition also are discussed.

Historical Population Declines Prompted Significant Genomic Erosion​ in the Northern and Southern White Rhinoceros (​ <i>Ceratotherium simum</i>)

Large vertebrates are extremely sensitive to anthropogenic pressures, and their populations are declining fast. The white rhinoceros (​Ceratotherium simum) is a paradigmatic case: this African megaherbivore suffered a remarkable population reduction in the last 150 years due to human activities. The two white rhino subspecies, the Northern (NWR) and the Southern white rhino (SWR), however, underwent opposite fates: the NWR vanished quickly after the onset of the decline, while the SWR recovered after a severe bottleneck. Such demographic events are predicted to have an erosive effect at the genomic level, linked to increased genetic drift and inbreeding. However, there is little empirical data available with which to reconstruct the subtleties of such processes. We therefore generated a whole-genome, temporal dataset consisting of 52 re-sequenced white rhino genomes, that represents both subspecies at two time windows throughout the past ~ 170 years. Our data not only reveals previously unknown population substructure within both subspecies, but allowed us to quantify the genomic erosion they underwent, with post-bottleneck white rhinos showing significantly lower levels of heterozygosity and higherinbreeding coefficients than pre-bottleneck individuals. Moreover, the effective population size (N​e​) has suffered a decrease of two and three orders of magnitude in the NWR and SWR, respectively. Our data provides empirical support for theoretical predictions about the genomic consequences ofshrinking populations, which is relevant for understanding the process of population extinction. Furthermore, our findings have the potential to inform tailored management approaches for the conservation of the remaining white rhinos.

Two-step extinction of Late Cretaceous marine vertebrates in northern Gulf of Mexico prolonged biodiversity loss prior to the Chicxulub impact

Recent studies on mass extinctions are often based on the global fossil record, but data from selected paleogeographic regions under a relatively constant paleoenvironmental setting can also provide important information. Eighty-nine marine vertebrate species, including cartilaginous and bony fish and marine reptiles, from northern Gulf of Mexico – located about 500 km from the Chicxulub crater – offer a unique opportunity to determine an extinction process during the last 20 million years of the Late Cretaceous. Our diversity data show two separate extinction events: (i) the ‘Middle Campanian Crisis’ (about 77 Mya) and (ii) the end-Maastrichtian (66 Mya) events. Whether this stepwise pattern of extinctions occurred locally or globally cannot be determined at present due to the lack of a dataset of the marine vertebrate record for reliable comparison. However, this stepwise pattern including the Middle Campanian and end-Maastrichtian events for, at least, a 13 million-year interval indicates long-term global marine environmental changes (e.g., regression, ocean water chemistry change). Because most Cretaceous marine vertebrates already disappeared in the Gulf of Mexico prior to the latest Maastrichtian, the Chicxulub Impact may not be considered as the most devastating extinction event for the community.

Learning mechanisms in nocebo hyperalgesia: the role of conditioning and extinction processes.

Nocebo hyperalgesia is a clinically relevant phenomenon and may be formed as a result of associative learning, implemented by classical conditioning. This study explored for the first time distinct nocebo conditioning methods and their consequences for nocebo attenuation methods. Healthy participants (N = 140) were recruited and randomized to the following nocebo hyperalgesia induction groups: conditioning with continuous reinforcement (CRF), conditioning with partial reinforcement (PRF), and a sham-conditioning control group. In the attenuation phase, counterconditioning was compared with extinction. During induction, participants experienced increased thermal pain in 100% of nocebo trials in the CRF groups, while in only 70% of nocebo trials in the PRF groups. During evocation, pain stimulation was equivalent across all trials. During attenuation, pain stimulation was decreased on nocebo trials relative to control trials for the counterconditioning groups, while pain remained equivalent across all trials for the extinction groups. Results showed that both PRF and CRF significantly induced nocebo hyperalgesia, but CRF was a more potent nocebo induction method, as compared to PRF. Counterconditioning was more effective than extinction in attenuating nocebo hyperalgesia. Neither CRF nor PRF resulted in resistance to extinction. However, compared with CRF, conditioning with PRF resulted in more resistance to counterconditioning. These findings demonstrate that the more ambiguous learning method of PRF can induce nocebo hyperalgesia and may potentially explain the treatment resistance and chronification seen in clinical practice. Further research is required to establish whether attenuation with counterconditioning is generalizable to clinical settings.

Environmental Drivers and Distribution Patterns of Carnivoran Assemblages (Mammalia: Carnivora) in the Americas: Past to Present

Understanding species distributions and the variation of assemblage structure in time and space are fundamental goals of biogeography and ecology. Here, we use an ecological niche modeling and macroecological approach in order to assess whether constraints patterns in carnivoran richness and composition structures in replicated assemblages through time and space should reflect environmental filtering through ecological niche constraints from the Last Inter-glacial (LIG), Last Glacial Maximum (LGM) to the present (C) time. Our results suggest a diverse distribution of carnivoran co-occurrence patterns at the continental scale as a result of spatial climatic variation as an important driver constrained by the ecological niches of the species. This influence was an important factor restructuring assemblages (more directly on richness than composition patterns) not only at the continental level, but also from regional and local scales and this influence was geographically different throughout the space in the continent. These climatic restrictions and disruption of the niche during the environmental changes at the LIG-LGM-C transition show a considerable shift in assemblage richness and composition across the Americas, which suggests an environmental filtering mainly during the LGM, explaining between 30 and 75% of these variations through space and time, with more accentuated changes in North than South America. LGM was likely to be critical in species functional adaptation and distribution and therefore on assemblage structuring and rearranging from continental to local scales through time in the continent. Still, extinction processes are the result of many interacting factors, where climate is just one part of the picture.

Vulnerability to Copper Smelter Emissions in Species of the Herb–Dwarf Shrub Layer: Role of Differences in the Type of Diaspore Dispersal

The type of diaspore dispersal may have a significant effect on the vulnerability of herbaceous plants to anthropogenic transformation of ecosystems. However, there is still no unified opinion on the relationship between the type of diaspore dispersal and the processes of extinction and colonization. Here, descriptions of vegetation performed in the zone of impact from the Middle Ural Copper Smelter in the periods of high and low emission levels (1995–1998 and 2014–2016, respectively) have been analyzed to test two hypotheses: (1) the type of diaspore dispersal has an effect on plant vulnerability, with the species whose diaspores are dispersed farther being less vulnerable to habitat transformation; and (2) irrespective of the type of dispersal, recolonization is less intense under high than under low pollution levels. It has been found that the species richness of all plant groups highly varies in space: it decreases sharply in the zone of heavy toxic loads, but localities with high species richness occur even under conditions of heavy pollution. With the increasing pollution level, the species diversity within plant groups on a mesoscale (hundreds of meters) decreases more strongly than that on a macroscale (kilometers). Species with different types of diaspore dispersal differ from each other both in sensitivity to pollution and in the capacity for recolonization after reduction of emissions, but the relationship between vulnerability and the distance of diaspore dispersal is ambiguous. High sensitivity to pollution and low recolonization capacity have been revealed in species characterized by either the lowest (autochores) or the highest dispersal distance (epi- and endozoochores), with anemochores being the least vulnerable. The diversity of most groups in the zone of heavy pollution has remained low over the past 20 years; some positive shifts have occurred in myrmecochores and typical anemochores, with the dynamics of the latter being independent of pollution level.

The local extinction and the nonlinear behaviors of a premixed methane/air flame under low-frequency acoustic excitation

The local extinction and the nonlinear behavior of a premixed methane/air flame under acoustic excitation are investigated experimentally. High-speed photography and high-speed schlieren imaging are used to investigate the oscillation characteristics of the premixed methane/air flame. The flame structure shows a periodic fluctuation when the acoustic excitation is performed to the flame. The local flame extinction can be observed during the flame evolution process. During the local flame extinction process, the flame is found to be cut into two components, then the downstream one extinguishes shortly. The Particle Image Velocimetry (PIV) results suggest that the lower velocity at the separation point is one of the reasons for the flame local extinction. The flame without the acoustic excitation oscillates with a dominant frequency of 18 Hz, which is shown by the schlieren images to be related to the evolution of the hot gas around the flame driven by the buoyant force. When the acoustic excitation frequency is 100 Hz, the structure of the hot gas is destroyed, meanwhile the amplitude of the nature frequency decreases significantly. The hot gas structure appears regularly with the increasing excitation frequency. As a result, the amplitude of the nature frequency also increases gradually. Proper Orthogonal Decomposition (POD) analysis shows that the dominant frequency of the flame without the acoustic excitation is mainly caused by the evolution of the production zone of the flame and the fluctuation of the flame tip. The evolution of the production zone is driven by the buoyant force, which indicates that the result from POD method is consistent with the conclusion obtained from the high-speed schlieren images. Two dominant modes are obtained when the excitation frequencies are 100 and 200 Hz. The two modes are mainly caused by the process of the local flame extinction and the increasing flame length.

Discovery of redundant free maximum disjoint Set-k-Covers for WSN life enhancement with evolutionary ensemble architecture

In the wireless sensor network, lifetime enhancement of network is a critical design issue for a wide number of applications. Along with ultra-low power technology, the computational approach in the development of several disjoint covers of sensors, such that each cover must provide the coverage of all targets, can be a more effective means for increasing the life span of the network. This enforces to maximize the number of possible disjoint covers, among available sensors in the network. Effectively this problem can be treated as a Set-K-Cover problem, which has been proven to be NP-complete. To make the solution more power-efficient, in this paper, the complexity of the problem has increased at a further level by expecting not only the upper bound of covers but also making the covers redundant free and formed with the minimal number of sensors. This problem can be considered as a search of multiple components where each component itself carried a multi-dimensional characteristic. In a natural system where evolution is the fundamental principle in the development of any entity, such kind of multi-component complex problem doesn’t handle at one stage. First, an integral approximated solution evolves and later each component evolves separately. This is the reason that for the Set-K-Cover problem, single stages of the various successful evolutionary algorithms have shown their limitation in achieving the upper bound of covers and in delivering redundant free solutions. In the past, some kind of sequential local scanning process has been integrated with evolutionary computation in the iteration for each cover to improve the performance. But discovered covers fail to meet objectives of upper bound and/or redundant free covers with the minimal number of sensors. Hence this research has explored the possibility of finding the solution through more closer to natural way i.e. only through evolution only (without local scanning process). To meet the desired objectives, in this paper an ensemble evolutionary concept has proposed which has delivered redundant free, the upper bound of covers with the minimum number of sensors. Evolutionary Ensemble architecture works at a different level in a cascaded manner to maximize the total possible number of disjoint covers and their refinement along with that there is a feedback mechanism to explore the new covers further if there is any. Based on the natural extinction process, an extinct operator has also introduced in the Genetic algorithm to increase the convergence rate and better exploration. Instead of fitness-oriented, equal opportunity for every parent in offspring creation was introduced to increase the diversity level. The performance results on different simulated networks confirm that without fail the proposed solution has achieved all objectives whereas various variants of Differential evolution and Genetic algorithms and Particle Swarm Optimization fail to deliver desired performances.

Pressure gradient tailoring effects on the mechanisms of bluff-body flame extinction

The mechanisms of flame blowout under pressure gradient effects are explored for a bluff-body stabilized flame. The blowout process is induced through equivalence ratio reduction from a lean stabilized flame to complete blowout. Simultaneous high-speed particle image velocimetry (PIV) and C2*/CH* chemiluminescence imaging diagnostics are used to obtain the instantaneous flame structure, vorticity field, equivalence ratio, and local strain rate during the extinction process. The goal is to elucidate the effect of flame-generated vorticity on lean flame extinction. Three test-sections configured as a nozzle, a rectangular duct, and a diffuser, are used to alter the downstream pressure gradient yielding high, nominal, and low magnitudes of flame-generated baroclinic torque. For all three configurations, the flame brush narrows and the shear layer vorticity expands in the transverse direction resulting in flame-shear interactions and extinction. The flame-shear layer interaction increases the strain rate along the flame; however, the strong flame-generated vorticity for the nozzle case delayed the strain rate increase by keeping the flame away from the shear layer the longest. The sharp increase in the Karlovitz number above unity caused by the sudden increase in the strain rate corresponds to the time of flame brush contraction and shear layer width expansion. It is shown that the downstream pressure gradient can either augment or attenuate the time required for the Karlovitz number to reach a critical value of unity, which is associated with local extinctions along the flame. In all of the test-section configurations, the flame-generated vorticity has a weak influence on the Bénard von Kármán (BVK) instability mode and its harmonics. The Strouhal number during blow-out remained relatively constant in all of the cases showing greater sensitivity to the shear layer length than to the BVK frequency.

Numerical study of methane combustion under moderate or intense low-oxygen dilution regime at elevated pressure conditions up to 8 atm

This paper investigates the effect of operating pressure (up to 8 atm) on the moderate or intense low-oxygen dilution (MILD) combustion of methane. Computational fluid dynamics (CFD) modeling was firstly conducted for a laboratory-scale combustor to obtain the distributions of temperature and minor species (CH2O and OH), and pollutants (CO and NO) emission under elevated operating pressures. To provide further insight into the heat release characteristics, flame structure, CO formation mechanism as well as extinction limit, a counterflow diffusion flame with hot oxidizer diluted oxidizer configuration was also modeled using detailed chemistry. The CFD modeling results show that increasing the operating pressure tends to increase both peak value and spatial gradient of the combustion temperature, and reduce the width of the reaction zone, indicating the departure of MILD combustion regime when using the identical burner. However, enhancing the internal flue gas recirculation by minimizing the air nozzle diameter can help sustain the MILD combustion regime. The kinetic modeling shows that MILD combustion features only positive heat release region, while traditional combustion exists both negative and positive heat release regions, where multiple peaks are observed. In addition, MILD combustion shows a dual oxygen consumption stage regardless of operating pressures. Simultaneously, MILD combustion exhibits a stretched S-curve of flame response without extinction and re-ignition processes, while traditional combustion presents obvious extinction and ignition points. These unique phenomena can be used for identifying MILD combustion regime in future work.

Hailstorm Detection by Satellite Microwave Radiometers

Passive microwave measurements from satellites have been used to identify the signature of hail in intense thunderstorms. The scattering signal of hailstones is typically observed as a strong depression of upwelling brightness temperatures from the cloud to the satellite. Although the relation between scattering signal and hail diameter is often assumed linear, in this work a logistic model is used which seems to well approximate the complexity of the radiation extinction process by varying the hail cross-section. A novel probability-based method for hail detection originally conceived for AMSU-B/MHS and now extended to ATMS, GMI, and SSMIS, is presented. The measurements of AMSU-B/MHS were analyzed during selected hailstorms over Europe, South America and the US to quantify the extinction of radiation due to the hailstones and large ice aggregates. To this aim, a probabilistic growth model has been developed. The validation analysis based on 12-year surface hail observations over the US (NOAA official reports) collocated with AMSU-B overpasses have demonstrated the high performance of the hail detection method in distinguishing between moderate and severe hailstorms, fitting the seasonality of hail patterns. The flexibility of the method allowed its experimental application to other microwave radiometers equipped with MHS-like frequency channels revealing a high level of portability.

Investigating the role of the amygdala orexin receptor 1 in memory acquisition and extinction in a rat model of PTSD

Understanding the mechanisms underlying memory is essential for the treatment of post-traumatic stress disorder (PTSD). Orexin, as a lateral hypothalamic (LH) neuropeptide, interferes with the stages of memory, primarily through the orexin receptor1 (Orx1R). The aim of this study was to evaluate the effects of amygdala Orx1R in the acquisition and extinction processes of PTSD modeled in animals.In three experiments, rats were divided into three groups: control (Naïve), shock (receiving a foot shock), and PTSD (experiencing Single prolonged stress (SPS) method). The first experiment aimed to evaluate LH activity in PTSD modeled rats. The second and third experiments aimed to evaluate the effects of Orx1R in the acquisition and extinction of fear memory in PTSD modeled animals. SB334867 (SB) or its solvent was microinjected into the amygdala and the rats were subjected to conditioning thereafter. In the second group, we used a single injection after conditioning. In the third group, we used three consecutive injections (one after each memory test). Some behaviors and Orx1R expression were evaluated.The freezing response was significantly longer in the PTSD group than on the control. Similarly, anxiety and sensitized fear were also intensified. CFos expression levels in LH was higher in the PTSD group. Inhibition of Orx1R in the amygdala significantly decreased memory acquisition, diminished anxiety, and decreased the sensitized fear in the SB group. Applying SB to the amygdala after each fear memory test significantly decreased freezing. Expression of Orx1R was significantly higher following fear conditioning.These results indicate a likely involvement of the orexin and amygdalar Orx1R in memory acquisition and in extinction of PTSD.

Deep-water channels in the lower Congo basin: Evolution of the geomorphology and depositional environment during the Miocene

Abstract Deep-water channel systems are an important component of the “source to sink” system from continental slope to deep-sea basin. They are also the critical reservoir type in deep-water hydrocarbon exploration. The study of geomorphology evolution, filling processes and controlling factors of the Miocene deep-water channel in the Lower Congo Basin is conducive to deepening our understanding of basin dynamics, and to improving the prediction accuracy of deep-water reservoirs. Based on 3D seismic data, cores, thin sections, well logging data, we study the Miocene seismic stratigraphic characteristics, deep-water sedimentary units, lithofacies and channel types. Using the techniques and means of seismic geomorphology, we discuss the occurrence, development, recession and extinction processes of channel complexes and controlling factors. The Miocene was divided into seven 3rd-order sequences. Each 3rd-order sequence is subdivided into two (lower/upper) seismic stratigraphy units, with initial flooding surface (FS) as the separated boundary. The seismic characteristics of the lower/upper unit suggest the occurrence of alternating turbidite/hemipelagic sedimentary units. Seismic units such as erosional surface, filling channel, levee, lobe, MTD and background slope deposits are described. Fifteen deep-water lithofacies are identified and they are determined to be composed of clay, silt, fine-coarse sand, gravel, and conglomerate. The deep-water channels in the study area are interpreted four types: single-stage erosional channel, single-stage aggradational channel, vertical aggradational channel complexes and lateral migration channel complexes. The different types of channel are the results of interaction of flow energy and accommodation space. On this basis, we propose that tectonic uplift is the driving force for the formation of the deep-water sandy channel system, and that high frequency sea-level fluctuation in West Africa controls the development of third-order sequences and restricts the scale of the deep-water sandstone accumulation. In addition, the avulsion processes controlled by climate variations are the main factors to influence channel complex filling process.

Fundamental utilitarianism and intergenerational equity with extinction discounting

Ramsey famously condemned discounting “future enjoyments” as “ethically indefensible”. Suppes enunciated an equity criterion which, when social choice is utilitarian, implies giving equal weight to all individuals’ utilities. By contrast, Arrow (Contemporary economic issues. International Economic Association Series. Palgrave Macmillan, London, 1999a; Discounting and Intergenerational Effects, Resources for the Future Press, Washington DC, 1999b) accepted, perhaps reluctantly, what he called Koopmans’ (Econometrica 28(2):287–309, 1960) “strong argument” implying that no equitable preference ordering exists for a sufficiently unrestricted domain of infinite utility streams. Here we derive an equitable utilitarian objective for a finite population based on a version of the Vickrey–Harsanyi original position, where there is an equal probability of becoming each person. For a potentially infinite population facing an exogenous stochastic process of extinction, an equitable extinction biased original position requires equal conditional probabilities, given that the individual’s generation survives the extinction process. Such a position is well-defined if and only if survival probabilities decline fast enough for the expected total number of individuals who can ever live to be finite. Then, provided that each individual’s utility is bounded both above and below, maximizing expected “extinction discounted” total utility—as advocated, inter alia, by the Stern Review on climate change—provides a coherent and dynamically consistent equitable objective, even when the population size of each generation can be chosen.

Effects of intranasal insulin as an enhancer of fear extinction: a randomized, double-blind, placebo-controlled experimental study.

Fear-extinction based psychotherapy (exposure) is the most effective method for treating anxiety disorders. Notwithstanding, since some patients show impairments in the unlearning of fear and insufficient fear remission, there is a growing interest in using cognitive enhancers as adjuvants to exposure. As insulin plays a critical role in stress processes and acts as a memory enhancer, this study aimed to assess the capacity of intranasal insulin to augment fear extinction. A double-blind, placebo-controlled differential fear-conditioning paradigm was conducted in 123 healthy participants (63 females). Pictures of faces with neutral expressions were used as conditioned stimuli and electric shocks as unconditioned stimuli. The paradigm consisted of four phases presented on three consecutive days: acquisition (day 1), extinction (day 2), reinstatement and re-extinction (day 3). A single intranasal dose of insulin (160 IU) or placebo was applied on day 2, 45 min before fear extinction. Skin conductance response (SCR), fear-potentiated startle (FPS) and expectancy ratings were assessed. During extinction, the insulin group (independent of sex) showed a significantly stronger decrease in differential FPS in comparison with the placebo group. Furthermore, a sex-specific effect was found for SCR, with women in the insulin group showing a greater decrease of differential SCR both at early extinction and at late re-extinction. Our results provide first evidence that intranasal insulin facilitates fear extinction processes and is therefore a promising adjuvant for extinction-based therapies in anxiety and related disorders. Sex-specific effects should be taken into consideration in future studies.