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The long-term trend in the diurnal temperature range over Sri Lanka from 1985 to 2017 and its association with total cloud cover and rainfall
No full textThis study is focused on studying the long-term trend of the diurnal temperature range (DTR) in three temperature zones in Sri Lanka using daily maximum and minimum temperature data set for the recent 33-year (1985–2017). We investigate the potential reasons for the long-term trend in the DTR by studying the response of the DTR to Total Cloud Cover (TCC) and rainfall on a seasonal basis. On an annual basis, results indicate that the DTR significantly decreased per decade by −0.14 °C, −0.16 °C, and −0.18 °C over the high elevation temperature zone (HT), low-elevation temperature zone one (LT-2), and low elevation temperature zone two (LT-2), respectively. The annual decreasing trend of DTR in three temperature zones is mainly due to the larger increase in minimum temperature over the HT (0.13 °C/decade), LT-1 (0.23 °C/decade), and LT-2 (0.14 °C/decade) zones than the maximum temperature from 1985 to 2017. Furthermore, a decreasing trend in DTR is observed during the southwest monsoon (SWM), first inter-monsoon (FIM), second inter-monsoon (SIM), and northeast monsoon (NEM) seasons, where the most prominent decreasing trend in HT, LT-1, and LT-2 is seen in NEM (−0.19 °C/decade), SIM (−0.24 °C/decade), and SWM (−0.40 °C/decade) seasons, respectively. The strong inverse correlation between the DTR and TCC in all seasons indicates that increasing TCC influences the decrease in DTR over the HT, LT-1, and LT-2 zones. Concomitant increasing trends in rainfall during NEM, FIM, and SIM seasons may be one of the possible causes of the DTR decreases in the aforementioned seasons over three temperature zones in Sri Lanka
Timing of Eocene compressional plate failure during subduction initiation, northern Zealandia, southwestern Pacific
No full textRapid onset of subduction tectonics across the western Pacific convergent margins in the early Eocene was followed by a slower phase of margin growth of the proto Tonga-Kermadec subduction system north of Zealandia during a middle Eocene phase to tectonic adjustment. We present new age constraints from International Ocean Discovery Program Expedition 371 borehole data on deformation events in northern Zealandian sediments that document the formation of the convergent margin boundary northwest of New Zealand. The deformation shows a shortening event that lasted up to 20 myr and acted over distances of ∼1000 km inboard of the evolving plate margin, just northwest of New Zealand. Multichannel seismic profiles tied to our new borehole sites show shortening occurred predominantly between 45 Ma and 35 Ma with some deformation related to slope failure continuing into the Oligocene. The termination of shortening is linked to opening of the backarc basins of the southwest Pacific and the migration of the Tonga-Kermadec Trench to the east which may have removed the structural evidence of the Eocene plate margin. Paleogene deformation observed inboard of the evolving proto Tonga-Kermadec subduction system indicates that the lithosphere of northern Zealandia, a region of thin continental crust, was strong enough to act as a stress guide. Compressive stresses that caused intra plate folding and faulting developed behind the initiating subduction system with the finite period of deformation indicating the time frame over which an active convergent margin lay along the northern margin of Zealandia
Stellar Companions to TESS Objects of Interest: A Test of Planet–Companion Alignment
No full textWe present a catalog of stellar companions to host stars of Transiting Exoplanet Survey Satellite Objects of Interest (TOIs) identified from a marginalized likelihood ratio test that incorporates astrometric data from the Gaia Early Data Release 3 catalog (EDR3). The likelihood ratio is computed using a probabilistic model that incorporates parallax and proper-motion covariances and marginalizes the distances and 3D velocities of stars in order to identify comoving stellar pairs. We find 172 comoving companions to 170 non-false-positive TOI hosts, consisting of 168 systems with two stars and 2 systems with three stars. Among the 170 TOI hosts, 54 harbor confirmed planets that span a wide range of system architectures. We conduct an investigation of the mutual inclinations between the stellar companion and planetary orbits using Gaia EDR3, which is possible because transiting exoplanets must orbit within the line of sight; thus, stellar companion kinematics can constrain mutual inclinations. While the statistical significance of the current sample is weak, we find that 73⁺¹⁴₋₂₀% of systems with Kepler-like architectures (R_P ≤ 4 R_⊕ and a 4 R_⊕) favor a perpendicular geometry (α= 89 ± 21∘) between the planet and companion. Moreover, the close-in giants with large stellar obliquities (planet-host misalignment) are also those that favor significant planet-companion misalignment
Altruism under Stress: Cortisol Negatively Predicts Charitable Giving and Neural Value Representations Depending on Mentalizing Capacity
No full textAltruism, defined as costly other-regarding behavior, varies considerably across people and contexts. One prominent context in which people frequently must decide on how to socially act is under stress. How does stress affect altruistic decision-making and through which neurocognitive mechanisms? To address these questions, we assessed neural activity associated with charitable giving under stress. Human participants (males and females) completed a charitable donation task before and after they underwent either a psychosocial stressor or a control manipulation, while their brain activity was measured using functional magnetic resonance imaging. As the ability to infer other people's mental states (i.e., mentalizing) predicts prosocial giving and may be susceptible to stress, we examined whether stress effects on altruism depend on participants' general capacity to mentalize, as assessed in an independent task. Although our stress manipulation per se had no influence on charitable giving, increases in the stress hormone cortisol were associated with reductions in donations in participants with high mentalizing capacity, but not in low mentalizers. Multivariate neural response patterns in the right dorsolateral prefrontal cortex (DLPFC) were less predictive of postmanipulation donations in high mentalizers with increased cortisol, indicating decreased value coding, and this effect mediated the (moderated) association between cortisol increases and reduced donations. Our findings provide novel insights into the modulation of altruistic decision-making by suggesting an impact of the stress hormone cortisol on mentalizing-related neurocognitive processes, which in turn results in decreased altruism. The DLPFC appears to play a key role in mediating this cortisol-related shift in altruism
CosmoVis: An Interactive Visual Analysis Tool for Exploring Hydrodynamic Cosmological Simulations
No full textWe introduce CosmoVis, an open source web-based visualization tool for the interactive analysis of massive hydrodynamic cosmological simulation data. CosmoVis was designed in close collaboration with astrophysicists to enable researchers and citizen scientists to share and explore these datasets, and to use them to investigate a range of scientific questions. CosmoVis visualizes many key gas, dark matter, and stellar attributes extracted from the source simulations, which typically consist of complex data structures multiple terabytes in size, often requiring extensive data wrangling. CosmoVis introduces a range of features to facilitate real-time analysis of these simulations, including the use of virtual skewers, simulated analogues of absorption line spectroscopy that act as spectral probes piercing the volume of gaseous cosmic medium. We explain how such synthetic spectra can be used to gain insight into the source datasets and to make functional comparisons with observational data. Furthermore, we identify the main analysis tasks that CosmoVis enables and present implementation details of the software interface and the client-server architecture. We conclude by providing details of three contemporary scientific use cases that were conducted by domain experts using the software and by documenting expert feedback from astrophysicists at different career levels
Ir-Catalyzed Asymmetric Allylic Alkylation of Dialkyl Malo-nates Enabling the Construction of Enantioenriched All-Carbon Quaternary Centers
No full textAn enantioselective iridium-catalyzed allylic alkylation of malonates with trisubstituted allylic electrophiles to form all-carbon quaternary stereocenters is reported. This cross-coupling reaction features unprecedented reactivity at ambient temperature, particularly for challenging fully alkyl-substituted allylic electrophiles, and enables the preparation of a wide range of enantio-enriched products in up to 93% yield and 97% ee. The products of this transformation can be readily converted to a number of valuable building blocks including vicinal quaternary stereodiads and β-quaternary acids. This method was also used to prepare an enantioenriched intermediate facilitating the asymmetric formal synthesis of the sporochnol family of natural products
Efficient CRISPR Mutagenesis in Sturgeon Demonstrates Its Utility in Large, Slow-Maturing Vertebrates
No full textIn the last decade, the CRISPR/Cas9 bacterial virus defense system has been adapted as a user-friendly, efficient, and precise method for targeted mutagenesis in eukaryotes. Though CRISPR/Cas9 has proven effective in a diverse range of organisms, it is still most often used to create mutant lines in lab-reared genetic model systems. However, one major advantage of CRISPR/Cas9 mutagenesis over previous gene targeting approaches is that its high efficiency allows the immediate generation of near-null mosaic mutants. This feature could potentially allow genotype to be linked to phenotype in organisms with life histories that preclude the establishment of purebred genetic lines; a group that includes the vast majority of vertebrate species. Of particular interest to scholars of early vertebrate evolution are several long-lived and slow-maturing fishes that diverged from two dominant modern lineages, teleosts and tetrapods, in the Ordovician, or before. These early-diverging or “basal” vertebrates include the jawless cyclostomes, cartilaginous fishes, and various non-teleost ray-finned fishes. In addition to occupying critical phylogenetic positions, these groups possess combinations of derived and ancestral features not seen in conventional model vertebrates, and thus provide an opportunity for understanding the genetic bases of such traits. Here we report successful use of CRISPR/Cas9 mutagenesis in one such non-teleost fish, sterlet Acipenser ruthenus, a small species of sturgeon. We introduced mutations into the genes Tyrosinase, which is needed for melanin production, and Sonic hedgehog, a pleiotropic developmental regulator with diverse roles in early embryonic patterning and organogenesis. We observed disruption of both loci and the production of consistent phenotypes, including both near-null mutants’ various hypomorphs. Based on these results, and previous work in lamprey and amphibians, we discuss how CRISPR/Cas9 F0 mutagenesis may be successfully adapted to other long-lived, slow-maturing aquatic vertebrates and identify the ease of obtaining and injecting eggs and/or zygotes as the main challenges
Inefficient Water Degassing Inhibits Ocean Formation on Rocky Planets: An Insight from Self-Consistent Mantle Degassing Models
No full textA sufficient amount of water is required at the surface to develop water oceans. A significant fraction of water, however, remains in the mantle during magma ocean solidification, and thus the existence of water oceans is not guaranteed even for exoplanets located in the habitable zone. To discuss the likelihood of ocean formation, we built two models to predict the rate of mantle degassing during the magma ocean stage and the subsequent solid-state convection stage. We find that planets with low H₂O/CO₂ ratios would not have a sufficient amount of surface water to develop water oceans immediately after magma ocean solidification, and the majority of the water inventory would be retained in the mantle during their subsequent evolution regardless of planetary size. This is because oceanless planets are likely to operate under stagnant lid convection, and for such planets, dehydration stiffening of the depleted lithospheric mantle would limit the rate of mantle degassing. In contrast, a significant fraction of CO₂ would already be degassed during magma ocean solidification. With a strong greenhouse effect, all surface water would exist as vapor, and water oceans may be absent throughout planetary evolution. Volatile concentrations in the bulk silicate Earth are close to the threshold amount for ocean formation, so if Venus shared similar concentrations, small differences in solar radiation may explain the divergent evolutionary paths of Earth and Venus
A Bounded-Confidence Model of Opinion Dynamics on Hypergraphs
No full textPeople's opinions evolve with time as they interact with their friends, family, colleagues, and others. In the study of opinion dynamics on networks, one often encodes interactions between people in the form of dyadic relationships, but many social interactions in real life are polyadic (i.e., they involve three or more people). In this paper, we extend an asynchronous bounded-confidence model (BCM) on graphs, in which nodes are connected pairwise by edges, to an asynchronous BCM on hypergraphs, in which arbitrarily many nodes can be connected by a single hyperedge. We show that our hypergraph BCM converges to consensus for a wide range of initial conditions for the opinions of the nodes, including for nonuniform and asymmetric initial opinion distributions. We also show that, under suitable conditions, echo chambers can form on hypergraphs with community structure. We demonstrate that the opinions of nodes can sometimes jump from one opinion cluster to another in a single time step; this phenomenon (which we call “opinion jumping'') is not possible in standard dyadic BCMs. Additionally, we observe a phase transition in the convergence time of our BCM on a complete hypergraph when the variance σ² of the initial opinion distribution equals the confidence bound c. We prove that the convergence time grows at least exponentially fast with the number of nodes when σ² > c and the initial opinions are normally distributed. Therefore, to determine the convergence properties of our hypergraph BCM when the variance and the number of hyperedges are both large, it is necessary to use analytical methods instead of relying only on Monte Carlo simulations
Alternating lysis and lysogeny is a winning strategy in bacteriophages due to Parrondo's paradox
No full textTemperate bacteriophages lyse or lysogenize host cells depending on various parameters of infection, a key one being the ratio of the number of free viruses to the number of host cells. However, the effect of different propensities of phages for lysis and lysogeny on phage fitness remains an open problem. We explore a nonlinear dynamic evolution model of competition between two phages, one of which is disadvantaged in both the lytic and lysogenic phases. We show that the disadvantaged phage can win the competition by alternating between the lytic and lysogenic phases, each of which individually is a “loser.” This counterintuitive result is analogous to Parrondo’s paradox in game theory, whereby individually losing strategies combine to produce a winning outcome. The results suggest that evolution of phages optimizes the ratio between the lysis and lysogeny propensities rather than the phage burst size in any individual phase. These findings are likely to broadly apply to the evolution of host–parasite interactions