Galactic Rotation Dynamics in f(T) gravity

We investigate galactic rotation curves in $f(T)$ gravity, where $T$ represents a torsional quantity. Our study centers on the particular Lagrangian $f(T)=T+\alpha{T^n}$, where $|n|\neq 1$ and $\alpha$ is a small unknown constant. To do this we treat galactic rotation curves as being composed from two distinct features of galaxies, namely the disk and the bulge. This process is carried out for several values of the index $n$. The resulting curve is then compared with Milky Way profile data to constrain the value of the index $n$ while fitting for the parameter $\alpha$. These values are then further tested on three other galaxies with different morphologies. On the galactic scale we find that $f(T)$ gravity departs from standard Newtonian theory in an important way. For a small range of values of $n$ we find good agreement with data without the need for exotic matter components to be introduced.Comment: 18 pages, 6 figures, Accepted for publication in the EPJ

Temperature, light and nitrate sensing coordinate Arabidopsis seed dormancy cycling resulting in winter and summer annual phenotypes

Seeds use environmental cues to sense the seasons and their surroundings to initiate the plants life cycle. Dormancy cycling underlying this process is extensively described, but the molecular mechanism is largely unknown. To address this we selected a range of representative genes from published array experiments in the laboratory and investigated their expression patterns in seeds of Arabidopsis ecotypes, having contrasting life cycles, over an annual dormancy cycle in the field. We show how mechanisms identified in the laboratory are coordinated in response to the soil environment to determine dormancy cycles that result in winter and summer annual phenotypes. Our results are consistent with a seed specific response to seasonal temperature patterns (temporal sensing) involving the gene DELAY OF GERMINATION1 (DOG1) that indicates the correct season; and concurrent temporally driven co-opted mechanisms that sense spatial signals i.e. nitrate via CBL-INTERACTING PROTEIN KINASE 23 (CIPK23) phosphorylation of the NITRATE TRANSPORTER 1 (NRT1.1) and light via PHYTOCHROME A (PHYA). In both ecotypes studied, when all three genes have low expression there is enhanced GIBBERELLIN 3 BETA-HYDROXYLASE 1 (GA3ox1) expression, exhumed seeds have the potential to germinate in the laboratory, and the initiation of seedling emergence occurs following soil disturbance (exposure to light) in the field. Unlike DOG1, expression of MOTHER of FLOWERING TIME (MFT) has an opposite thermal response in seeds of the two ecotypes indicating a role in determining their different dormancy cycling phenotypes

Linear and nonlinear optical pulse characterisation

Developmental work on the generation and measurement of ultrashort pulses has been performed. A colliding pulse, passively mode-locked (CPM) ring dye laser has been investigated by spectral analysis and the nonlinear technique of second harmonic generation autocorrelation. Two systems for the intracavity compensation of group velocity dispersion (GVD) have been experimentally compared in the CPM laser. Initially one scheme, utilising Gires-Toumois interferometers, has achieved pulse durations of 64 fs. A second technique employing a four-prism sequence within the cavity gave typical pulse durations of -40 fs and focussing adjustments within the jets achieved durations as short as 19 fs for the first time. A realtime interferometric autocorrelator was constructed and detailed theoretical work has been performed to model the resultant fringe resolved autocorrelations as a function of pulseshape and frequency chirp. Spectral and autocorrelation analysis of the CPM laser led to the inference that the laser pulse intensity profiles were distinctly asymmetric. The main sources of frequency chirp within the laser cavity were assessed in order to find possible explanations for this type of laser behaviour. The linear pulse measurement technique employing synchroscan streak cameras was also critically assessed in terms of the available temporal resolutions as a function of phase noise in the RF deflection signal. Two streak tube designs, the Photochron II and the Photochron IV, have been experimentally compared employing the CPM laser as a test pulse source. Optimisation of the synchronisation circuitry has allowed the notable achievement of a temporal resolution of 0.93ps for the Photochron IV streak camera. A computer-interfaced readout system incorporating a charge coupled device (CCD) sensor has been developed which allows the recording of synchroscan streak events with a digitisation accuracy up to 12 bits. Preliminary experimentation was also performed to investigate the feasibility of incorporating a electron sensitive CCD structure within the envelope of the streak camera. It is intended that such a streak camera will be incorporated in a spaceborne laser ranging system and a theoretical assessment of the expected instrument performance has been performed. The above investigations have direct relevance to other types of ultrashort pulse sources and their application in optical communications, time-resolved spectroscopy and ultrafast electrooptic sampling

Modified Gravity Research

Five small articles by each author: 1 The Gravity Research Group by Jackson Levi Said 2 Cosmology and Gravity: The dark side of the universe by Gabriel Farrugia 3 Galactic Rotation Dynamics in Modifi ed Gravity by Andrew Finch 4 Exotic Stars by Mark Pacepeer-reviewe

Injury deaths in Australian sport and recreation: Identifying and assessing priorities for prevention

Introduction Sport and recreation is beneficial for health and wellbeing but comes with a probability of loss, including occasional fatal injuries. Following high-profile injury deaths in Australia, concerns are raised regarding the safety of sport participation. To understand the scale and scope of injury deaths, and identify potential prevention opportunities, the aim of this investigation was to describe the number and nature of fatal injuries in Australian sport and recreation. Methods This is a retrospective cohort study of injury deaths reported between 1 July 2000 to 31 December 2019 using data from the National Coronial Information System, Australia. Unintentional deaths with an external cause, where the activity was recorded as sport and exercise during leisure time were included. Drowning deaths were excluded. Presented are the number and % of cases by age, sex, sport, broad cause and annual crude death rate (population). Results There were 1192 deaths, averaging 63 per year. Deaths were mostly in males (84.4%), with the largest proportion in people aged 15–24 years (23.1%). Wheeled motor (26.9%) and non-motor (16.2%) sports accounted for the highest proportion of cases. The primary mechanism of death was most commonly blunt force (85.4%), followed by piercing/penetrating force (5.0%). The years 2001 and 2005 recorded the highest crude injury death rate (2001, n = 92, 0.47 per 100,000 population; 2005, n = 95, 0.47 per 100,000 population). Conclusions On average, there is more than one injury death per week in a sport or recreation setting in Australia. Cases occurred in many sports and recreation activities, including those generally considered to be safe (e.g. individual athletic activities, team ball sports.) Detailed investigation of the coronial recommendations that are present within each case is now needed to understand and identify potential prevention opportunities