The New Approach to the Preparation of Polyacrylamide-Based Hydrogels: Initiation of Polymerization of Acrylamide with 1,3-Dimethylimidazolium (Phosphonooxy-)Oligosulphanide under Drying Aqueous Solutions

The new initiator of the polymerization of acrylamide, leading to the formation of crosslinked polyacrylamide, was discovered. The structure of the synthesized polyacrylamide was characterized by XRD, 1Н NMR, and 13С NMR spectroscopy. It was shown that 1,3-dimethylimidazolium (phosphonooxy-)oligosulphanide is able to initiate radical polymerization under drying aqueous solutions of acrylamide, even at room temperature. According to XRF data, the synthesized polyacrylamide gel contains 0.28 wt% of sulphur. The formed polymer network has a low crosslinking density and a high equilibrium degree of swelling. The swelling rate of polyacrylamide gel in water corresponds to the first order kinetic equation with the rate constant 6.2 × 10−2 min−1. The initiator is promising for combining acrylamide polymerization with the processes of gel molding and drying.

Preparation of a photocurable hydrogel with adjustable mechanical properties for 3D printing

Purpose This paper aims to show a series of hydrogels with adjustable mechanical properties, which can be cured quickly with visible light. The hydrogel is prepared conveniently with hydroxyethyl acrylate, cross-linker, gelatin and photoinitiator, and can be printed into certain 3D patterns with the direct ink write (DIW) 3D printer designed and developed by the research group. Design/methodology/approach In this paper, the authors designed a composite sensitization initiation system that is suitable for hydrogels. The concentration of photoinitiator, gelatin and cross-linker was studied to optimize the curing efficiency and adjust the mechanical properties. A DIW 3D printer was designed for the printing of hydrogel. Pre-gel solution was loaded into printer for printing into established models. The models were made and sliced with software. Findings The hydrogels can be cured efficiently with 405-nm visible light. While adding various content of gelatin and cross-linker, the mechanical properties of hydrogels show from soft and fragile (elastic modulus of 121.18 kPa and work of tension of 218.11 kJ·m−3) to rigid and tough (elastic modulus of 505.15 kPa and work of tension of 969.00 kJ·m−3). The hydrogels have high capacity of water absorption. With the DIW 3D printer, pre-gel hydrogel solution can be printed into objects with certain dimension. Originality/value In this work, a composite sensitization initiation system was designed, and fast curing hydrogels with adjustable mechanical properties had been prepared conveniently, which has high equilibrium water content and 3D printability with the DIW 3D printer.

A nearby transiting rocky exoplanet that is suitable for atmospheric investigation

Spectroscopy of transiting exoplanets can be used to investigate their atmospheric properties and habitability. Combining radial velocity (RV) and transit data provides additional information on exoplanet physical properties. We detect a transiting rocky planet with an orbital period of 1.467 days around the nearby red dwarf star Gliese 486. The planet Gliese 486 b is 2.81 Earth masses and 1.31 Earth radii, with uncertainties of 5%, as determined from RV data and photometric light curves. The host star is at a distance of ~8.1 parsecs, has a J-band magnitude of ~7.2, and is observable from both hemispheres of Earth. On the basis of these properties and the planet’s short orbital period and high equilibrium temperature, we show that this terrestrial planet is suitable for emission and transit spectroscopy.

Recycling-Oriented Design of the Al-Zn-Mg-Ca Alloys

Approaches to the design of recycling-tolerant Al-Zn-Mg alloys were formulated to be achieved via combined Ca, Fe, and Si, and appropriate solidification conditions and heat treatment. A CalPhaD calculation and experimental study were employed for analysis of the Al-8%Zn-3%Mg alloy doped with 1–2%Ca, 0.5%Fe, and 0.5%Si. The Al-8%Zn-3%Mg-1%Ca-0.5%Fe-0.5%Si (AlZnMg1CaFeSi) alloy was preliminarily found to be promising since it showed a high equilibrium solidus, and an as-cast structure including curved phases (Al), Al3Fe, Al2CaSi2, Al10CaFe2, and (Al, Zn)4Ca; favouring a further spheroidization response during a two-step annealing at 450 °C, 3 h + 520 °C, 3 h. Furthermore, the alloy showed an excellent age-hardening response (195 HV, T6), which did not yield the values of the base alloy and outperformed the values of the other experimental counterparts. Regarding feasibility, 80% reduction hot rolling was successfully conducted, as well as a brief comparison with commercial 6063 impurity-tolerant alloys. As it showed qualitatively similar structural patterns and Fe and Si alloying opportunities, the AlZnMg1CaFeSi alloy may serve as a sustainable basis for the further development of high-strength aluminum alloys tailored for manufacture from scrap materials.

Polygenic Adaptation in a Population of Finite Size

Polygenic adaptation in response to selection on quantitative traits has become an important topic in evolutionary biology. Here we review the recent literature on models of polygenic adaptation. In particular, we focus on a model that includes mutation and both directional and stabilizing selection on a highly polygenic trait in a population of finite size (thus experiencing random genetic drift). Assuming that a sudden environmental shift of the fitness optimum occurs while the population is in a stochastic equilibrium, we analyze the adaptation of the trait to the new optimum. When the shift is not too large relative to the equilibrium genetic variance and this variance is determined by loci with mostly small effects, the approach of the mean phenotype to the optimum can be approximated by a rapid exponential process (whose rate is proportional to the genetic variance). During this rapid phase the underlying changes to allele frequencies, however, may depend strongly on genetic drift. While trait-increasing alleles with intermediate equilibrium frequencies are dominated by selection and contribute positively to changes of the trait mean (i.e., are aligned with the direction of the optimum shift), alleles with low or high equilibrium frequencies show more of a random dynamics, which is expected when drift is dominating. A strong effect of drift is also predicted for population size bottlenecks. Our simulations show that the presence of a bottleneck results in a larger deviation of the population mean of the trait from the fitness optimum, which suggests that more loci experience the influence of drift.

Inflation of migrated hot Jupiters

ABSTRACT The observed low densities of gas giant planets with a high equilibrium temperature (hot Jupiters) can be simulated in models when a fraction of the surface radiation is deposited deeper in the interior. Meanwhile, migration theories suggest that hot Jupiters formed further away from their host star and migrated inward. We incorporate disc migration in simulations of the evolving interior of hot Jupiters to determine whether migration has a long-lasting effect on the inflation of planets. We quantify the difference between the radius of a migrated planet and the radius of a planet that formed in situ as the radius discrepancy. We remain agnostic about the physical mechanism behind interior heating, but assume it scales with the received stellar flux by a certain fraction. We find that the change in irradiation received from the host star while the planet is migrating can affect the inflation and final radius of the planet. Models with a high fraction of energy deposited in the interior (>5 per cent) show a significant radius discrepancy when the deposit is at higher pressures than $P=1 \, \mathrm{bar}$. For a smaller fraction of 1 per cent, there is no radius discrepancy for any deposit depth. We show that a uniform heating mechanism can cause different rates of inflation, depending on the migration history. If the forthcoming observations on mean densities and atmospheres of gas giants give a better indication of a potential heating mechanism, this could help to constrain the prior migration of such planets.

Making Moves Matter: Experimental Evidence on Incentivizing Bureaucrats through Performance-Based Postings

Bureaucracies often post staff to better or worse locations, ostensibly to provide incentives. Yet we know little about whether this works, with heterogeneity in preferences over postings impacting effectiveness. We propose a performance-ranked serial dictatorship mechanism, whereby bureaucrats sequentially choose desired locations in order of performance. We evaluate this using a two-year field experiment with 525 property tax inspectors in Pakistan. The mechanism increases annual tax revenue growth by 30–41 percent. Inspectors whom our model predicts face high equilibrium incentives under the scheme indeed increase performance more. Our results highlight the potential of periodic merit-based postings in enhancing bureaucratic performance. (JEL C93, D73, H71, H83, J45, M54, O17)

MASCARA-2 b

In this paper we present MASCARA-2 b, a hot Jupiter transiting the mV = 7.6 A2 star HD 185603. Since early 2015, MASCARA has taken more than 1.6 million flux measurements of the star, corresponding to a total of almost 3000 h of observations, revealing a periodic dimming in the flux with a depth of 1.3%. Photometric follow-up observations were performed with the NITES and IAC80 telescopes and spectroscopic measurements were obtained with the Hertzsprung SONG telescope. We find MASCARA-2 b orbits HD 185603 with a period of 3.4741119-0.000006+0.000005 days at a distance of 0.057 ± 0.006 au, has a radius of 1.83 ± 0.07 RJ and place a 99% upper limit on the mass of <17 MJ. HD 185603 is a rapidly rotating early-type star with an effective temperature of 8980-130+90 K and a mass and radius of 1.89-0.05+0.06 M⊙, 1.60 ± 0.06 R⊙, respectively. Contrary to most other hot Jupiters transiting early-type stars, the projected planet orbital axis and stellar spin axis are found to be aligned with λ = 0.6 ± 4°. The brightness of the host star and the high equilibrium temperature, 2260 ± 50 K, of MASCARA-2 b make it a suitable target for atmospheric studies from the ground and space. Of particular interest is the detection of TiO, which has recently been detected in the similarly hot planets WASP-33 b and WASP-19 b.