Magnetic fields on young, solar-type stars

This thesis describes an investigation aimed at using spectropolarimetric observations of the magnetic fields of young solar-type stars to improve the understanding of the early development of solar and stellar dynamos and activity cycles. The emergence of stellar dynamos is important in understanding the evolution of young stars (and activity effects on any attendant emerging planetary systems). Stars were selected on the basis of their rapid rotation and activity. HD 106506, HD 76298, HD 35256, HD 29613 and EK Draconis formed the primary targets. Spectropolarimetric data were obtained with the Anglo-Australian Telescope, the Canada-France-Hawaii Telescope and the T´elescope Bernard Lyot with supporting broadband photometric data from the Mount Kent Observatory. Reduction and analysis of the data were performed to produce magnetic field detections, spot occupancy and magnetic field maps, differential rotation values, chromospheric flux estimates, starspot light curves and other measurements. Several results were obtained, as follows: (1) A distributed dynamo fundamentally different to the modern Sun’s interface-layer dynamo appears widespread in young solartype stars, with all targets displaying significant surface azimuthal fields consistent with the dynamo operating throughout the convection zone. (2) All stars showed significant enhancement in chromospheric activity that appears to be primarily a function of rapid stellar rotation (3) Multi-epoch observations of the young solar analogue EK Draconis demonstrated a rapidly evolving magnetic field that could not be explained due to differential rotation alone, and hints at the presence of temporal variability due to the rapid evolution from a strongly toroidal magnetic field ( approx 80%) to a more balanced poloidal-toroidal configuration in three months of observations. (4) The differential rotation of HD 29615, with a rotational shear delta omega = 0.58+ 0.14 −0.12 rad d−1 is one of the largest yet observed through x-squared minimisation method, making this star a useful test case for the theory and modelling of dynamos in young solar-type stars

Magnetic fields and differential rotation on the pre-main sequence

Maps of magnetic field topologies of rapidly rotating stars obtained over the last decade or so have provided unique insight into the operation of stellar dynamos. However, for solar-type stars many of the targets imaged to date have been lower-mass zero-age main sequence stars. We present magnetic maps and differential rotation measurements of two-higher mass pre-main sequence stars HD 106506 (~10 Myrs) and HD 141943 (~15 Myrs). These stars should evolve into mid/late F-stars with predicted high differential rotation and little magnetic activity. We investigate what effect the extended convection zones of these pre-main sequence stars has on their differential rotation and magnetic topologies. ©2009 American Institute of Physic

Assessing the Suitability of Black Soldier Fly Castings Produced from Piggery Waste as a Fertilizer

Black Soldier Fly (Hermetia illucens, BSF) farming provides an alternative waste management solution on piggeries by utilising manure to produce a high protein insect meal, whilst the fly castings (frass) are a valuable fertiliser

Biodiversity of living, non marine, thrombolites of Lake Clifton, Western Australia

<p>Lake Clifton in Western Australia is recognized as a critically endangered ecosystem and the only thrombolite reef in the southern hemisphere. There have been concerns that increases in salinity and nutrient run-off have significantly impacted upon the thrombolite microbial community. Here we used cultivation-independent molecular approaches to characterize the microbial diversity of the thrombolites at Lake Clifton. The most dominant phyla currently represented are the Proteobacteria with significant populations of Bacteroidetes and Firmicutes. Cyanobacteria, previously invoked as the main drivers of thrombolite growth, represent only a small fraction (∼1–3% relative abundance) of the microbial community. We report an increase in salinity and nitrogen levels at Lake Clifton that may be contributing to a change in dominant microbial populations. This heightens concerns about the long-term health of the Lake Clifton thrombolites; future work is needed to determine if phyla now dominating this system are capable of the required mineral precipitation for continued thrombolite growth.</p

Football Game Program 3 1965

Football Game Program 3 196

Bacterial processes associated with soil C and N following application of compost and manure to dairy pasture at the beginning and end of the growing season

This study investigated the impact of dairy manure and compost on bacterial community composition and functional diversity in a dairy pasture in south-western Australia

Scaling of Early Social Cognitive Skills in Typically Developing Infants and Children with Autism Spectrum Disorder

We delineate the sequence that typically developing infants pass tasks that assess different early social cognitive skills considered precursors to theory-of-mind abilities. We compared this normative sequence to performance on these tasks in a group of autistic (AUT) children. 86 infants were administered seven tasks assessing intention reading and shared intentionality (Study 1). Infants responses followed a consistent developmental sequence, forming a four-stage scale. These tasks were administered to 21 AUT children (Study 2), who passed tasks in the same sequence. However, performance on tasks that required following others’ eye gaze and cooperating with others was delayed. Findings indicate that earlier-developing skills provide a foundation for later-developing skills, and difficulties in acquiring some early social cognitive skills in AUT children

Discovery of the magnetic field in the B1/B2V star sigma Lupi

The ultraviolet stellar wind lines of the photometrically periodic variable early B-type star sigma Lupi were found to behave very similarly to what has been observed in known magnetic B stars, although no periodicity could be determined. AAT spectropolarimetric measurements with SEMPOL were obtained. We detected a longitudinal magnetic field with varying strength and amplitude of about 100 G with error bars of typically 20 G. This type of variability supports an oblique magnetic rotator model. We fold the equivalent width of the 4 usable UV spectra in phase with the well-known photometric period of 3.019 days, which we identify with the rotation period of the star. The magnetic field variations are consistent with this period. Additional observations with ESPaDOnS attached to the CFHT strongly confirmed this discovery, and allowed to determine a precise magnetic period. Like in the other magnetic B stars the wind emission likely originates in the magnetic equatorial plane, with maximum emission occurring when a magnetic pole points towards the Earth. The 3.0182 d magnetic rotation period is consistent with the photometric period, with maximum light corresponding to maximum magnetic field. No helium or other chemical peculiarity is known for this object.Comment: 2 pages, 2 figures, to appear in the proceedings of IAU Symposium 272, Active OB stars - structure, evolution, mass loss, and critical limit

Standard- versus intermediate-dose enoxaparin for anti-factor Xa guided thromboprophylaxis in critically ill patients with COVID-19

Abstract The prevalence of venous thromboembolism (VTE) is high in critically ill patients with COVID-19. Dosing of Low Molecular Weight Heparin (LMWH) for thromboprophylaxis in patients with severe COVID-19 is subject to ongoing debate. In this brief report, we describe our study where we retrospectively examined the efficacy of standard- versus intermediate-dosing of enoxaparin in attaining and maintaining accepted prophylactic levels of anti-Factor Xa (anti-FXa) in critically ill patients with COVID-19. We collected data for all patients with confirmed COVID-19 who were treated with enoxaparin for thromboprophylaxis in a single Intensive Care Unit (ICU) in the United Kingdom between 31st March and 16th November 2020. Standard-dose of enoxaparin was 40 mg subcutaneously once daily for patients with normal renal function and body weight between 50 and 100 kg; the intermediate-dose was 40 mg subcutaneously twice daily. Anti-FXa peak concentrations between 0.2-0.4 IU/ml were considered appropriate for thromboprophylaxis. Age, sex, weight, Body Mass Index, APACHE II score, ICU length of stay, initial P/F ratio and creatinine were not statistically significantly different between standard- and intermediate-dose thromboprophylaxis cohorts. In the standard-dose group, the median initial anti-FXa level was 0.13 (interquartile range 0.06-0.18) compared to 0.26 (0.21-0.33) in the intermediate-dose cohort (p < 0.001). On repeated measurement, in the standard dose cohort, 44 of 95 (46%) anti-FXa levels were < 0.2 IU/ml compared with 24 of 132 (18%) levels in the intermediate-dose cohort even after dose-adjustment. There was one radiologically confirmed pulmonary embolism (PE) on computed tomography pulmonary angiogram during hospital admission in each cohort. Our study supports starting intermediate-dose thromboprophylaxis for critically ill patients with COVID-19 to achieve anti-FXa levels in the accepted thromboprophylactic range although further study is required to investigate whether anti-FXa guided thromboprophylaxis is safe and effective in reducing the incidence of VTEs in critically ill patients with COVID-19