Powering Mercury's dynamo

The presence of the global magnetic field of Mercury has implications for the interior structure of the planet and its thermal evolution. We use a thermal evolution model to explore the conditions under which excess entropy is available to drive a convective dynamo. The current state of the core is strongly affected by its sulfur concentration and the viscosity of the overlying mantle. A present-day dynamo is difficult to achieve. The minimum rate of entropy production required to drive a dynamo is attained in only the most optimistic models, and requires present-day mantle convection. An additional entropy source such as the addition of a radiogenic heat source in the core increases the probability of a present-day dynamo. Given the uncertainty, more specific characterization of the planet's interior and magnetic field is required to alleviate ambiguities in the original Mariner 10 observations

On a direct approach to quasideterminant solutions of a noncommutative KP equation

A noncommutative version of the KP equation and two families of its solutions expressed as quasideterminants are discussed. The origin of these solutions is explained by means of Darboux and binary Darboux transformations. Additionally, it is shown that these solutions may also be verified directly. This approach is reminiscent of the wronskian technique used for the Hirota bilinear form of the regular, commutative KP equation but, in the noncommutative case, no bilinearising transformation is available.Comment: 11 page

Characterization of a process for the in-furnace reduction of NOx, SO2, and HCl by carboxylic salts of calcium

Calcium magnesium acetate has been assessed as an agent for the reduction of NOx, SO2, and HCl, at the pilot scale, in a down-fired combustor operating at 80 kWth. In addition to this, the chemical and physical processes that occur during heating have been investigated. Benchmarking of calcium magnesium acetate with a suite of five other carboxylic salts (calcium magnesium acetate, calcium propionate, calcium acetate, calcium benzoate, magnesium acetate, and calcium formate) has been performed. NOx reduction involves the volatile organic content of the carboxylic salt being released at temperatures of >1000 °C, where the reaction of CHi radicals with NO under fuel-rich conditions can result in some of the NO forming N2 in a “reburning” process. Thermogravimetry-Fourier transform infrared (TG-FTIR) studies identified the nature of the decomposition products from the low- and high-temperature decompositions. In addition, the rate of weight losses were studied to investigate the influence of the organic decomposition on NOx reduction by reburning. In-furnace reductions of SO2 and HCl are aided by the highly porous, particulate residue, which results from the in situ drying, pyrolysis, and calcination processes. Simultaneous reduction of all three pollutants was obtained, and a synergy between SO2 and HCl capture was identified. A mechanism for this inter-relationship has been proposed. Sorbent particle characterization has been performed by collecting the calcined powder from a spray pyrolysis reactor and compared with those produced from a suite of pure carboxylic salts. Physical properties (including porosity, surface area, and decomposition behavior) have been discussed, relative to reductions in NOx and acid gas emissions

Prediction of biomass ash fusion behaviour by the use of detailed characterization methods coupled with thermodynamic analysis.

Ash deposition such as slagging and fouling on boiler tube surfaces is an inevitable, though undesirable consequence of burning solid fuels in boilers. The role of fuel characteristics, in affecting the form and severity of the problem, is significant. In recent years, biomass fuels have gained increasing popularity as an environmentally friendly source of energy in power plants all over the world. This study is based on characterising the fusion behaviour of four biomass fuels (pine wood, peanut shells, sunflower stalk and miscanthus) using ash fusion temperature (AFT) tests, simultaneous thermal analysis (STA) of fuel ashes, calculation of empirical indices and predicting ash melting behaviour with the help of thermodynamic equilibrium calculations. The AFT results failed to show any clear trend between fusion temperature and high alkali content of biomass. STA proved useful in predicting the different changes occurring in the ash. Empirical indices predicted high slagging and fouling hazards for nearly all the biomass samples and this was supported by the possible existence of a melt phase at low temperatures as predicted by thermodynamic calculations

How does temperature affect splicing events? Isoform switching of splicing factors regulates splicing of <i>LATE ELONGATED HYPOCOTYL</i> (<i>LHY</i>)

One of the ways in which plants can respond to temperature is via alternative splicing (AS). Previous work showed that temperature changes affected the splicing of several circadian clock gene transcripts. Here we investigated the role of RNA‐binding splicing factors (SFs) in temperature‐sensitive alternative splicing (AS) of the clock gene LATE ELONGATED HYPOCOTYL (LHY). We characterised, in wild type plants, temperature‐associated isoform switching and expression patterns for SF transcripts from a high‐resolution temperature and time series RNA‐seq experiment. In addition we employed quantitative RT‐PCR of SF mutant plants to explore the role of the SFs in cooling‐associated AS of LHY. We show that the splicing and expression of several SFs responds sufficiently rapidly and sensitively to temperature changes to contribute to the splicing of the 5’UTR of LHY. Moreover the choice of splice site in LHY was altered in some SF mutants. The splicing of the 5’UTR region of LHY has characteristics of a molecular thermostat, where the ratio of transcript isoforms is sensitive to temperature changes as modest as 2°C and is scalable over a wide dynamic range of temperature. Our work provides novel insight into SF‐mediated coupling of the perception of temperature to post‐transcriptional regulation of the clock

Constraining Ceres' interior from its Rotational Motion

Context. Ceres is the most massive body of the asteroid belt and contains about 25 wt.% (weight percent) of water. Understanding its thermal evolution and assessing its current state are major goals of the Dawn Mission. Constraints on internal structure can be inferred from various observations. Especially, detailed knowledge of the rotational motion can help constrain the mass distribution inside the body, which in turn can lead to information on its geophysical history. Aims. We investigate the signature of the interior on the rotational motion of Ceres and discuss possible future measurements performed by the spacecraft Dawn that will help to constrain Ceres' internal structure. Methods. We compute the polar motion, precession-nutation, and length-of-day variations. We estimate the amplitudes of the rigid and non-rigid response for these various motions for models of Ceres interior constrained by recent shape data and surface properties. Results. As a general result, the amplitudes of oscillations in the rotation appear to be small, and their determination from spaceborne techniques will be challenging. For example, the amplitudes of the semi-annual and annual nutations are around ~364 and ~140 milli-arcseconds, and they show little variation within the parametric space of interior models envisioned for Ceres. This, combined with the very long-period of the precession motion, requires very precise measurements. We also estimate the timescale for Ceres' orientation to relax to a generalized Cassini State, and we find that the tidal dissipation within that object was probably too small to drive any significant damping of its obliquity since formation. However, combining the shape and gravity observations by Dawn offers the prospect to identify departures of non-hydrostaticity at the global and regional scale, which will be instrumental in constraining Ceres' past and current thermal state. We also discuss the existence of a possible Chandler mode in the rotational motion of Ceres, whose potential excitation by endogenic and/or exogenic processes may help detect the presence of liquid reservoirs within the asteroid.Comment: submitted to Astronomy and Astrophysic

Isostatic equilibrium in spherical coordinates and implications for crustal thickness on the Moon, Mars, Enceladus, and elsewhere

Isostatic equilibrium is commonly defined as the state achieved when there are no lateral gradients in hydrostatic pressure, and thus no lateral flow, at depth within the lower viscosity mantle that underlies a planetary body's outer crust. In a constant-gravity Cartesian framework, this definition is equivalent to the requirement that columns of equal width contain equal masses. Here we show, however, that this equivalence breaks down when the spherical geometry of the problem is taken into account. Imposing the "equal masses" requirement in a spherical geometry, as is commonly done in the literature, leads to significant lateral pressure gradients along internal equipotential surfaces, and thus corresponds to a state of disequilibrium. Compared with the "equal pressures" model we present here, the "equal masses" model always overestimates the compensation depth--by ~27% in the case of the lunar highlands and by nearly a factor of two in the case of Enceladus.Comment: 23 pages of text; 3 figures; accepted for publication in GR

Assessment of the Impact of Potential Tetracycline Exposure on the Phenotype of Aedes aegypti OX513A: Implications for Field Use

Aedes aegypti is the primary vector of dengue fever, a viral disease which has an estimated incidence of 390 million infections annually. Conventional vector control methods have been unable to curb the transmission of the disease. We have previously reported a novel method of vector control using a tetracycline repressible self-limiting strain of Ae. aegypti OX513A which has achieved >90% suppression of wild populations.We investigated the impact of tetracycline and its analogues on the phenotype of OX513A from the perspective of possible routes and levels of environmental exposure. We determined the minimum concentration of tetracycline and its analogues that will allow an increased survivorship and found these to be greater than the maximum concentration of tetracyclines found in known Ae. aegypti breeding sites and their surrounding areas. Furthermore, we determined that OX513A parents fed tetracycline are unable to pre-load their progeny with sufficient antidote to increase their survivorship. Finally, we studied the changes in concentration of tetracycline in the mass production rearing water of OX513A and the developing insect.Together, these studies demonstrate that potential routes of exposure of OX513A individuals to tetracycline and its analogues in the environment are not expected to increase the survivorship of OX513A