Evolutionary pathways toward gigantism in sharks and rays

Through elasmobranch (sharks and rays) evolutionary history, gigantism evolved multiple times in phylogenetically distant species, some of which are now extinct. Interestingly, the world's largest elasmobranchs display two specializations found never to overlap: filter feeding and mesothermy. The contrasting lifestyles of elasmobranch giants provide an ideal case study to elucidate the evolutionary pathways leading to gigantism in the oceans. Here, we applied a phylogenetic approach to a global dataset of 459 taxa to study the evolution of elasmobranch gigantism. We found that filter feeders and mesotherms deviate from general relationships between trophic level and body size, and exhibit significantly larger sizes than ectothermic‐macropredators. We confirm that filter feeding arose multiple times during the Paleogene, and suggest the possibility of a single origin of mesothermy in the Cretaceous. Together, our results elucidate two main evolutionary pathways that enable gigantism: mesothermic and filter feeding. These pathways were followed by ancestrally large clades and facilitated extreme sizes through specializations for enhancing prey intake. Although a negligible percentage of ectothermic‐macropredators reach gigantic sizes, these species lack such specializations and are correspondingly constrained to the lower limits of gigantism. Importantly, the very adaptive strategies that enabled the evolution of the largest sharks can also confer high extinction susceptibility

Rain evaporation rate estimates from dual-wavelength lidar measurements and intercomparison against a model analytical solution

Rain evaporation, while significantly contributing to moisture and heat cloud budgets, is a still poorly understood process with few measurements presently available. Multiwavelength lidars, widely employed in aerosols and clouds studies, can also provide useful information on the microphysical characteristics of light precipitation, for example, drizzle and virga. In this paper, lidar measurements of the median volume raindrop diameter and rain evaporation rate profiles are compared with a model analytical solution. The intercomparison reveals good agreement between the model and observations, with a correlation between the profiles up to 65% and a root-mean-square error up to 22% with a 5% bias. Larger discrepancies are due to radiosonde soundings different air masses and model assumptions no more valid along the profile as nonsteady atmosphere and/or appearance of collision–coalescence processes. Nevertheless, this study shares valuable information to better characterize the rain evaporation processes

Dynamics, cation conformation and rotamers in guanidinium ionic liquids with ether groups

Ionic liquids are modern materials with a broad range of applications, including electrochemical devices, the exploitation of sustainable resources and chemical processing. Expanding the chemical space to include novel ion classes allows for the elucidation of novel structure-property relationships and fine tuning for specific applications. We prepared a set of ionic liquids based on the sparsely investigated pentamethyl guanidinium cation with a 2-ethoxy-ethyl side chain in combination with a series of frequently used anions. The resulting properties are compared to a cation with a pentyl side chain lacking ether functionalization. We measured the thermal transitions and transport properties to estimate the performance and trends of this cation class. The samples with imide-type anions form liquids at ambient temperature, and show good transport properties, comparable to imidazolium or ammonium ionic liquids. Despite the dynamics being significantly accelerated, ether functionalization of the cation favors the formation of crystalline solids. Single crystal structure analysis, ab initio calculations and variable temperature nuclear magnetic resonance measurements (VT-NMR) revealed that cation conformations for the ether- and alkyl-chain-substituted are different in both the solid and liquid states. While ether containing cations adopt compact, curled structures, those with pentyl side chains are linear. The Eyring plot revealed that the curled conformation is accompanied by a higher activation energy for rotation around the carbon-nitrogen bonds, due to the coordination of the ether chain as observed by VT-NMR

Comparison of surface and column measurements of aerosol scattering properties over the western North Atlantic Ocean at Bermuda

Light scattering by size-resolved aerosols in near-surface air at Tudor Hill, Bermuda, was measured between January and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized in parallel with a micro-pulse lidar (MPL) and an automated sun–sky radiometer. Comparisons were made between extensive aerosol parameters in the column, such as the lidar-retrieved extinction at 400 m and the aerosol optical depth (AOD), and scattering was measured with a surface nephelometer. Comparisons were also made for intensive parameters such as the Ångström exponent and calculations using AERONET(Aerosol Robotic Network)-derived aerosol physical parameters (size distribution, index of refraction) and Mie theory, and the ratio of submicron scattering to total scattering for size-segregated nephelometer measurements. In these comparisons the <i>r</i>² was generally around 0.50. Data were also evaluated based on back trajectories. The correlation between surface scattering and lidar extinction was highest for flows when the surface scattering was dominated by smaller particles and the flow had a longer footprint over land then over the ocean. The correlation of AOD with surface scatter was similar for all flow regimes. There was also no clear dependence of the atmospheric lapse rate, as determined from a nearby radiosonde station, on flow regime. The Ångström exponent for most flow regimes was 0.9–1.0, but for the case of air originating from North America, but with significant time over the ocean, the Ångström exponent was 0.57 ± 0.18. The submicron fraction of aerosol near the surface (<i>R</i>_sub-surf) was significantly greater for the flows from land (0.66 ± 0.11) than for the flows which spent more time over the ocean (0.40 ± 0.05). When comparing <i>R</i>_sub-surf and the column-integrated submicron scattering fraction, <i>R</i>_sub-col, the correlation was similar, <i>r</i>² = 0.50, but <i>R</i>_sub-surf was generally less than <i>R</i>_sub-col, indicating more large particles contributing to light scattering at the surface, contrary to conditions over continents and for polluted continental transport over the ocean. In general, though, the marginal correlations indicate that the column optical properties are weakly correlated with the surface optical measurements. Thus, if it is desired to associate aerosol chemical/physical properties with their optical properties, it is best to use optical and chemical/physical measurements with both collected at the surface or both collected in the column

Science lives: School choices and ‘natural tendencies’

An analysis of 12 semi-structured interviews with university-based scientists and non-scientists illustrates their life journeys towards, or away from, science and the strengths and impact of life occurrences leading them to choose science or non-science professions. We have adopted narrative approaches and used Mezirow's transformative learning theory framework. The areas of discussion from the result have stressed on three main categories that include ‘smooth transition’, ‘incremental wavering transition' and ‘transformative transition’. The article concludes by discussing the key influences that shaped initial attitudes and direction in these people through natural inclination, environmental inspirations and perceptions of science

Clear-column radiative closure during ACE-Asia: Comparison of multiwavelength extinction derived from particle size and composition with results from Sun photometry

From March to May 2001, aerosol size distributions and chemical compositions were measured using differential mobility analyzers (DMA), an aerodynamic particle sizer (APS), Micro-Orifice Uniform Deposit Impactors (MOUDI), and denuder samplers onboard the Twin Otter aircraft as part of the Aerosol Characterization Experiment (ACE)-Asia campaign. Of the 19 research flights, measurements on four flights that represented different aerosol characteristics are analyzed in detail. Clear-column radiative closure is studied by comparing aerosol extinctions predicted using in situ aerosol size distribution and chemical composition measurements to those derived from the 14-wavelength NASA Ames Airborne Tracking Sun photometer (AATS-14). In the boundary layer, pollution layers, and free troposphere with no significant mineral dust present, aerosol extinction closure was achieved within the estimated uncertainties over the full range of wavelengths of AATS-14. Aerosol extinctions predicted based on measured size distributions also reproduce the wavelength dependence derived from AATS-14 data. Considering all four flights, the best fit lines yield Predicted/Observed ratios in boundary and pollution layers of 0.97 ± 0.24 and 1.07 ± 0.08 at λ = 525 nm and 0.96 ± 0.21 and 1.08 ± 0.08 at λ = 1059 nm, respectively. In free troposphere dust layers, aerosol extinctions predicted from the measured size distributions were generally smaller than those derived from the AATS-14 data, with Predicted/Observed ratios of 0.65 ± 0.06 and 0.66 ± 0.05 at 525 and 1059 nm, respectively. A detailed analysis suggests that the discrepancy is likely a result of the lack of the knowledge of mineral dust shape as well as variations in aerosol extinction derived from AATS-14 data when viewing through horizontally inhomogeneous layers

Can spacetime curvature induced corrections to Lamb shift be observable?

The Lamb shift results from the coupling of an atom to vacuum fluctuations of quantum fields, so corrections are expected to arise when the spacetime is curved since the vacuum fluctuations are modified by the presence of spacetime curvature. Here, we calculate the curvature-induced correction to the Lamb shift outside a spherically symmetric object and demonstrate that this correction can be remarkably significant outside a compact massive astrophysical body. For instance, for a neutron star or a stellar mass black hole, the correction is $\sim$ 25% at a radial distance of $4GM/c^2$, $\sim$ 16% at $10GM/c^2$ and as large as $\sim$ 1.6% even at $100GM/c^2$, where $M$ is the mass of the object, $G$ the Newtonian constant, and $c$ the speed of light. In principle, we can look at the spectra from a distant compact super-massive body to find such corrections. Therefore, our results suggest a possible way of detecting fundamental quantum effects in astronomical observations.Comment: 13 pages, 3 figures, slight title change, clarifications and more discussions added, version to be published in JHE

Clear-Column Radiative Closure During ACE-Asia: Comparison of Multiwavelength Extinction Derived from Particle Size and Composition with Results from Sun Photometry

From March to May 2001, aerosol size distributions and chemical compositions were measured using differential mobility analyzers (DMA), an aerodynamic particle sizer (APS), Micro-Orifice Uniform Deposit Impactors (MOUDI), and denuder samplers onboard the Twin Otter aircraft as part of the Aerosol Characterization Experiment (ACE)-Asia campaign. Of the 19 research flights, measurements on four flights that represented different aerosol characteristics are analyzed in detail. Clear-column radiative closure is studied by comparing aerosol extinctions predicted using in situ aerosol size distribution and chemical composition measurements to those derived from the 14-wavelength NASA Ames Airborne Tracking Sun photometer (AATS-14). In the boundary layer, pollution layers, and free troposphere with no significant mineral dust present, aerosol extinction closure was achieved within the estimated uncertainties over the full range of wavelengths of AATS-14. Aerosol extinctions predicted based on measured size distributions also reproduce the wavelength dependence derived from AATS-14 data. Considering all four flights, the best fit lines yield Predicted/Observed ratios in boundary and pollution layers of 0.97 ± 0.24 and 1.07 ± 0.08 at λ = 525 nm and 0.96 ± 0.21 and 1.08 ± 0.08 at λ = 1059 nm, respectively. In free troposphere dust layers, aerosol extinctions predicted from the measured size distributions were generally smaller than those derived from the AATS-14 data, with Predicted/Observed ratios of 0.65 ± 0.06 and 0.66 ± 0.05 at 525 and 1059 nm, respectively. A detailed analysis suggests that the discrepancy is likely a result of the lack of the knowledge of mineral dust shape as well as variations in aerosol extinction derived from AATS-14 data when viewing through horizontally inhomogeneous layers

Adsorption and wettability study of methyl ester sulphonate on precipitated asphaltene

Asphaltene precipitation from crude oil and its subsequent aggregation forms solid, which preferentially deposit on rock surfaces causing formation damage and wettability changes leading to loss of crude oil production. To resolve this problem, asphaltene inhibitor has been injected into the formation to prevent the precipitation of asphaltene. Asphaltene inhibitors that are usually employed are generally toxic and non-biodegradable. This paper presents a new environmentally friendly asphaltene inhibitor (methyl ester sulphonate), an anionic surfactant, which has excellent sorption on formation rock surfaces. Result from adsorption study validated by Langmuir and Freundlich models indicate a favourable adsorption. At low volumes injected, methyl ester sulphonate is capable of reverting oil-wet sandstone surface to water-wet surface. Biodegradability test profile shows that for concentrations of 100-5000ppm it is biodegradable by 65-80%