Magnetic Structure of Rapidly Rotating FK Comae-Type Coronae

We present a three-dimensional simulation of the corona of an FK Com-type rapidly rotating G giant using a magnetohydrodynamic model that was originally developed for the solar corona in order to capture the more realistic, non-potential coronal structure. We drive the simulation with surface maps for the radial magnetic field obtained from a stellar dynamo model of the FK Com system. This enables us to obtain the coronal structure for different field topologies representing different periods of time. We find that the corona of such an FK Com-like star, including the large scale coronal loops, is dominated by a strong toroidal component of the magnetic field. This is a result of part of the field being dragged by the radial outflow, while the other part remains attached to the rapidly rotating stellar surface. This tangling of the magnetic field,in addition to a reduction in the radial flow component, leads to a flattening of the gas density profile with distance in the inner part of the corona. The three-dimensional simulation provides a global view of the coronal structure. Some aspects of the results, such as the toroidal wrapping of the magnetic field, should also be applicable to coronae on fast rotators in general, which our study shows can be considerably different from the well-studied and well-observed solar corona. Studying the global structure of such coronae should also lead to a better understanding of their related stellar processes, such as flares and coronal mass ejections, and in particular, should lead to an improved understanding of mass and angular momentum loss from such systems.Comment: Accepted to ApJ, 10 pages, 6 figure

The preparation and characterisation of monomeric and linked metal carbonyl clusters containing the closo-Si2Co4 pseudo-octahedral core

PhSiH3 reacts with [Co₄(CO)₁₂] at 50 °C in hydrocarbon solvents to give [(µ₄-SiPh)₂Co₄(CO)₁₁], 2c, shown by an X-ray crystal structure determination to have a pseudo-octahedral Si₂Co₄ core. Substituted aryl-silanes behaved similarly. Mixtures of PhSiH₃, H₃SiC₆H₄SiH₃ and [Co₄(CO)₁₂] in a ca. 2 1 2 ratio gave the dimeric cluster [{Co₄(µ₄-SiPh)(CO)₁₁Si}₂C₆H₄], 3a, which has the two Si₂Co₄ cores linked by a C₆H₄ group to give a rigid molecule which an X-ray structure analysis shows to be over 23 Å long. Related dimers linked by –(CH₂)₈– groups were isolated from mixtures of PhSiH₃, α ,ω-(H₃Si)₂(CH₂)₈ and [Co₄(CO)₁₂]. Electrochemical studies show the two cluster units in 3a do not interact electronically

A Characterization of Different Spark Regimes for Ignition Delay Comparison with Conventional Spark Plugs

poster abstractThe introduction of plasma into combustion and ignition processes has continuously proved to be advantageous when compared to the conventional spark ignition in a wide range of categories. From the capability to ignite leaner mixtures and improve fuel economy to an effective reduction of hazardous emissions and ignition delay, the benefits of integrating non-equilibrium plasma can be utilized for numerous applications including hot jet ignition. Detailed design specifications for the electrode configuration, circuit schematic, and combustion rig are developed and presented. Using a CCD camera and high performance oscilloscope, this paper aims to identify, characterize, and compare the different effects of frequency and pulse width of a driver circuit on the plasma sparks quantitatively in terms of the current, voltage, and energy attributes. Four different plasma regimes are investigated with frequencies ranging from 5.44 Hz to 95.46 kHz and pulse energies ranging from 168 μJ to 14.42 J. The maximum voltage and current characteristics of the plasmas indicate a glow discharge referencing previous experiments. Future work is laid out for a comparison of the ignition progression between a non-thermal plasma system and a traditional spark with using Schlieren imaging

Differential expression analysis for sequence count data

*Motivation:* High-throughput nucleotide sequencing provides quantitative readouts in assays for RNA expression (RNA-Seq), protein-DNA binding (ChIP-Seq) or cell counting (barcode sequencing). Statistical inference of differential signal in such data requires estimation of their variability throughout the dynamic range. When the number of replicates is small, error modelling is needed to achieve statistical power.

*Results:* We propose an error model that uses the negative binomial distribution, with variance and mean linked by local regression, to model the null distribution of the count data. The method controls type-I error and provides good detection power. 

*Availability:* A free open-source R software package, _DESeq_, is available from the Bioconductor project and from "http://www-huber.embl.de/users/anders/DESeq":http://www-huber.embl.de/users/anders/DESeq

A simple approach to the visible-light photoactivation of molecular metal oxides

This study explores a new method to maximize the visible-light-driven photocatalytic performance of organic–inorganic hybrid polyoxometalates (POMs). Experimental and theoretical investigations of a family of phosphonate-substituted POMs show that modification of grafted organic moieties can be used to tune the electronic structure and photoactivity of the metal oxide component. Unlike fully inorganic polyoxotungstates, these organic–inorganic hybrid species are responsive to visible light and function as photocatalysts (λ > 420 nm) in the decomposition of a model environmental pollutant. The degree of photoactivation is shown to be dependent on the nature of the inductive effect exerted by the covalently grafted substituent groups. This study emphasizes the untapped potential that lies in an orbital engineering approach to hybrid-POM design and helps to underpin the next generation of bespoke, robust, and cost-effective molecular metal oxide photoactive materials and catalysts

The healthiness of food and beverages on price promotion at promotional displays: A cross-sectional audit of australian supermarkets

Supermarket environments can strongly influence purchasing decisions. Price promotions are recognised as a particularly persuasive tactic, but the healthiness of price promotions in prominent in-store locations is understudied. This study compared the prevalence and magnitude of price promotions on healthy and unhealthy food and beverages (foods) displayed at prominent in-store locations within Australian supermarkets, including analyses by supermarket group and area-level socio-economic position. A cross-sectional in-store audit of price promotions on foods at key display areas was undertaken in 104 randomly selected stores from major Australian supermarket groups (Woolworths, Coles, Aldi and independents) in Victoria, Australia. Of the display space dedicated to foods with price promotions, three of the four supermarket groups had a greater proportion of display space devoted to unhealthy (compared to healthy) foods at each promotional location measured (end of aisles: 66%; island bins: 53%; checkouts: 88%). Aldi offered very few price promotions. Few measures varied by area-level socio-economic position. This study demonstrated that price promotions at prominent in-store locations in Australian supermarkets favoured unhealthy foods. Marketing of this nature is likely to encourage the purchase of unhealthy foods, highlighting the need for retailers and policy-makers to consider addressing in-store pricing and placement strategies to encourage healthier food environments

A rigorous real time Feynman Path Integral and Propagator

We will derive a rigorous real time propagator for the Non-relativistic Quantum Mechanic $L^2$ transition probability amplitude and for the Non-relativistic wave function. The propagator will be explicitly given in terms of the time evolution operator. The derivation will be for all self-adjoint nonvector potential Hamiltonians. For systems with potential that carries at most a finite number of singularity and discontinuities, we will show that our propagator can be written in the form of a rigorous real time, time sliced Feynman path integral via improper Riemann integrals. We will also derive the Feynman path integral in Nonstandard Analysis Formulation. Finally, we will compute the propagator for the harmonic oscillator using the Nonstandard Analysis Feynman path integral formuluation; we will compute the propagator without using any knowledge of classical properties of the harmonic oscillator

Generation of whole genome sequences of new Cryptosporidium hominis and Cryptosporidium parvum isolates directly from stool samples

BACKGROUND: Whole genome sequencing (WGS) of Cryptosporidium spp. has previously relied on propagation of the parasite in animals to generate enough oocysts from which to extract DNA of sufficient quantity and purity for analysis. We have developed and validated a method for preparation of genomic Cryptosporidium DNA suitable for WGS directly from human stool samples and used it to generate 10 high-quality whole Cryptosporidium genome assemblies. Our method uses a combination of salt flotation, immunomagnetic separation (IMS), and surface sterilisation of oocysts prior to DNA extraction, with subsequent use of the transposome-based Nextera XT kit to generate libraries for sequencing on Illumina platforms. IMS was found to be superior to caesium chloride density centrifugation for purification of oocysts from small volume stool samples and for reducing levels of contaminant DNA. RESULTS: The IMS-based method was used initially to sequence whole genomes of Cryptosporidium hominis gp60 subtype IbA10G2 and Cryptosporidium parvum gp60 subtype IIaA19G1R2 from small amounts of stool left over from diagnostic testing of clinical cases of cryptosporidiosis. The C. parvum isolate was sequenced to a mean depth of 51.8X with reads covering 100 % of the bases of the C. parvum Iowa II reference genome (Bioproject PRJNA 15586), while the C. hominis isolate was sequenced to a mean depth of 34.7X with reads covering 98 % of the bases of the C. hominis TU502 v1 reference genome (Bioproject PRJNA 15585). The method was then applied to a further 17 stools, successfully generating another eight new whole genome sequences, of which two were C. hominis (gp60 subtypes IbA10G2 and IaA14R3) and six C. parvum (gp60 subtypes IIaA15G2R1 from three samples, and one each of IIaA17G1R1, IIaA18G2R1, and IIdA22G1), demonstrating the utility of this method to sequence Cryptosporidium genomes directly from clinical samples. This development is especially important as it reduces the requirement to propagate Cryptosporidium oocysts in animal models prior to genome sequencing. CONCLUSION: This represents the first report of high-quality whole genome sequencing of Cryptosporidium isolates prepared directly from human stool samples

Local models of stellar convection: Reynolds stresses and turbulent heat transport

We study stellar convection using a local three-dimensional MHD model, with which we investigate the influence of rotation and large-scale magnetic fields on the turbulent momentum and heat transport. The former is studied by computing the Reynolds stresses, the latter by calculating the correlation of velocity and temperature fluctuations, both as functions of rotation and latitude. We find that the horisontal correlation, Q_(theta phi), capable of generating horisontal differential rotation, is mostly negative in the southern hemisphere for Coriolis numbers exceeding unity, corresponding to equatorward flux of angular momentum in accordance with solar observations. The radial component Q_(r phi) is negative for slow and intermediate rotation indicating inward transport of angular momentum, while for rapid rotation, the transport occurs outwards. Parametrisation in terms of the mean-field Lambda-effect shows qualitative agreement with the turbulence model of Kichatinov & R\"udiger (1993) for the horisontal part H \propto Q_(theta phi)/cos(theta), whereas for the vertical part, V \propto Q_(r phi)/sin(theta), agreement only for intermediate rotation exists. The Lambda-coefficients become suppressed in the limit of rapid rotation, this rotational quenching being stronger for the V component than for H. We find that the stresses are enhanced by the presence of the magnetic field for field strengths up to and above the equipartition value, without significant quenching. Concerning the turbulent heat transport, our calculations show that the transport in the radial direction is most efficient at the equatorial regions, obtains a minimum at midlatitudes, and shows a slight increase towards the poles. The latitudinal heat transport does not show a systematic trend as function of latitude or rotation.Comment: 26 pages, 20 figures, final published version. For a version with higher resolution figures, see http://cc.oulu.fi/~pkapyla/publ.htm

High Contrast Imaging of the Close Environment of HD 142527 -

Context. It has long been suggested that circumstellar disks surrounding young stars may be the signposts of planets, and still more since the recent discoveries of embedded substellar companions. The planet-disk interaction may create, according to models, large structures, gaps, rings or spirals, in the disk. In that sense, the Herbig star HD 142527 is particularly compelling as, its massive disk displays intriguing asymmetries that suggest the existence of a dynamical peturber of unknown nature. Aims. Our goal was to obtain deep thermal images of the close circumstellar environment of HD 142527 to re-image the reported close-in structures (cavity, spiral arms) of the disk and to search for stellar and substellar companions that could be connected to their presence. Results. The circumstellar environment of HD 142527 is revealed at an unprecedented spatial resolution down to the sub arcsecond level for the first time at 3.8 microns. Our images reveal important radial and azimuthal asymmetries which invalidate an elliptical shape for the disk as previously proposed. It rather suggests a bright inhomogeneous spiral arm plus various fainter spiral arms. We also confirm an inner cavity down to 30 AU and two important dips at position angles of 0 and 135 deg. The detection performance in angular differential imaging enables the exploration of the planetary mass regime for projected physical separations as close as 40 AU. The use of our detection map together with Monte Carlo simulations sets stringent constraints on the presence of planetary mass, brown dwarf or stellar companions as a function of the semi-major axis. They severely constrain the presence of massive giant planets with semi-major axis beyond 50AU, i.e. probably within the large disk's cavity that radially extends up to 145 AU or even further outside.Comment: 8 pages, 7 figures, accepted in A&