Photography and the paradigm of the trace

The idea that photographs can be explained as traces made by the things they depict has been a recurring paradigm in theories about the nature of the photographic medium. Walter Benjamin, Charles Sanders Peirce, Susan Sontag, Andre Bazin and Roland Barthes are a few of the many theorists who have used the paradigm of the trace to explain the nature of photographs. The paradigm can also be argued to have been a significant influence in the work of prominent artists such as Gerhard Richter, Adam Fuss and Cornelia Parker whose work has explored the photographic medium. Through an exegesis and accompanying photobook this thesis addresses the question as to why the trace has proven to be such an enduring paradigm for explaining the nature of photographs, and how the paradigm can be perceived in art practice in recent decades. The subject of the photograph as a trace is investigated through conducting a review of the history of theoretical uses of the paradigm of the trace to explain the nature of photography. The work of visual artists whose practice can be seen as in agreement with or in opposition to these theoretical approaches was also reviewed. In conjunction with this research a series of photographic works was produced using alternative photographic techniques including pinhole photography, photographs and techniques combining digital film projection and phosphorescent plates. Seeing photographs as traces links these forms of image making to one of humanity’s earliest “discoveries”, the ability to interpret traces found in nature. Through such a connection photographs can be seen as a continuation of humanity’s ability to read traces and thereby understand and deal with the passage of time, to buttress processes of memory and belief. This thesis thereby explores a key means through which the photographic object is explained and understood, at a time when the use of photographs as a means of documenting and understanding the world is expanding at an exponential rate

Determining the Gamma-Ray Burst Rate as a Function of Redshift

We exploit the 14 gamma-ray bursts (GRBs) with known redshifts z and the 7 GRBs for which there are constraints on z to determine the GRB rate R_{GRB}(z), using a method based on Bayesian inference. We find that, despite the qualitative differences between the observed GRB rate and estimates of the SFR in the universe, current data are consistent with R_{GRB}(z) being proportional to the SFR.Comment: To appear in Procs. of Gamma-Ray Bursts in the Afterglow Era: 2nd Workshop, 3 pages, 3 figures, LaTe

Thermonuclear .Ia Supernovae from Helium Shell Detonations: Explosion Models and Observables

During the early evolution of an AM CVn system, helium is accreted onto the surface of a white dwarf under conditions suitable for unstable thermonuclear ignition. The turbulent motions induced by the convective burning phase in the He envelope become strong enough to influence the propagation of burning fronts and may result in the onset of a detonation. Such an outcome would yield radioactive isotopes and a faint rapidly rising thermonuclear ".Ia" supernova. In this paper, we present hydrodynamic explosion models and observable outcomes of these He shell detonations for a range of initial core and envelope masses. The peak UVOIR bolometric luminosities range by a factor of 10 (from 5e41 - 5e42 erg/s), and the R-band peak varies from M_R,peak = -15 to -18. The rise times in all bands are very rapid (<10 d), but the decline rate is slower in the red than the blue due to a secondary near-IR brightening. The nucleosynthesis primarily yields heavy alpha-chain elements (40Ca through 56Ni) and unburnt He. Thus, the spectra around peak light lack signs of intermediate mass elements and are dominated by CaII and TiII features, with the caveat that our radiative transfer code does not include the non-thermal effects necessary to produce He features.Comment: Accepted for publication in The Astrophysical Journal; 9 pages, 9 figures; v2: Minor changes to correct typos and clarify conten

Pre-hospital paediatric intubation

Thesis (M.Sc.(Med.))--University of the Witwatersrand, Faculty of Health Sciences, 2014

Molinism: Explaining our Freedom Away

Molinists hold that there are contingently true counterfactuals about what agents would do if put in specific circumstances, that God knows these prior to creation, and that God uses this knowledge in choosing how to create. In this essay we critique Molinism, arguing that if these theses were true, agents would not be free. Consider Eve’s sinning upon being tempted by a serpent. We argue that if Molinism is true, then there is some set of facts that fully explains both Eve’s action and everything else Eve does that influences that action; and that if this is the case, Eve does not act freely. The first premise of this argument follows from the explanatory relations the Molinist is committed to, and the second premise follows from libertarian intuitions about free will

Batched Ranged Random Integer Generation

Pseudorandom values are often generated as 64-bit binary words. These random words need to be converted into ranged values without statistical bias. We present an efficient algorithm to generate multiple independent uniformly-random bounded integers from a single uniformly-random binary word, without any bias. In the common case, our method uses one multiplication and no division operations per value produced. In practice, our algorithm can more than double the speed of unbiased random shuffling for small to moderately large arrays

Collective Dynamics Differentiates Functional Divergence in Protein Evolution

Protein evolution is most commonly studied by analyzing related protein sequences and generating ancestral sequences through Bayesian and Maximum Likelihood methods, and/or by resurrecting ancestral proteins in the lab and performing ligand binding studies to determine function. Structural and dynamic evolution have largely been left out of molecular evolution studies. Here we incorporate both structure and dynamics to elucidate the molecular principles behind the divergence in the evolutionary path of the steroid receptor proteins. We determine the likely structure of three evolutionarily diverged ancestral steroid receptor proteins using the Zipping and Assembly Method with FRODA (ZAMF). Our predictions are within ∼2.7 Å all-atom RMSD of the respective crystal structures of the ancestral steroid receptors. Beyond static structure prediction, a particular feature of ZAMF is that it generates protein dynamics information. We investigate the differences in conformational dynamics of diverged proteins by obtaining the most collective motion through essential dynamics. Strikingly, our analysis shows that evolutionarily diverged proteins of the same family do not share the same dynamic subspace, while those sharing the same function are simultaneously clustered together and distant from those, that have functionally diverged. Dynamic analysis also enables those mutations that most affect dynamics to be identified. It correctly predicts all mutations (functional and permissive) necessary to evolve new function and ∼60% of permissive mutations necessary to recover ancestral function

Position statement: Pre-hospital rapid sequence intubation

The Professional Board for Emergency Care at the Health Professions Council of South Africa (HPCSA) has approved pre-hospital rapid sequence intubation (RSI) as part of the scope of practice for registered emergency care practitioners (ECPs). RSI is an advanced airway management process that facilitates endotracheal intubation in adults and children. Features of this technique include pre-oxygenation, rapid pharmacological induction of unconsciousness, and neuromuscular blockade to enable the placement of an endotracheal tube. RSI has become widespread as the procedure of choice for definitive airway management by pre- and in-hospital emergency care personnel worldwide. In the emergency department setting, RSI is superior to intubation with deep sedation, a technique not incorporating pharmacological paralysis as part of the intubation sequence. For this reason, the implementation of RSI in the pre-hospital environment is supported, provided that it is practised within an appropriate framework of clinical governance

Determining the Gamma-Ray Burst Rate as a Function of Redshift

We exploit the 14 gamma-ray bursts (GRBs) with known redshifts z and the 7 GRBs for which there are constraints on z to determine the GRB rate R_(GRB)(z), using a method based on Bayesian inference. We find that, despite the qualitative differences between the observed GRB rate and estimates of the SFR in the universe, current data are consistent with R_(GRB)(z) being proportional to the SFR

An Active Galactic Nucleus Caught in the Act of Turning Off and On

We present the discovery of an active galactic nucleus (AGN) that is turning off and then on again in the z = 0.06 galaxy SDSS J1354+1327. This episodic nuclear activity is the result of discrete accretion events that could have been triggered by a past interaction with the companion galaxy that is currently located 12.5 kpc away. We originally targeted SDSS J1354+1327 because its Sloan Digital Sky Survey spectrum has narrow AGN emission lines that exhibit a velocity offset of 69 km s−1 relative to systemic. To determine the nature of the galaxy and its velocity-offset emission lines, we observed SDSS J1354+1327 with Chandra/ACIS, Hubble Space Telescope/Wide Field Camera 3, Apache Point Observatory optical longslit spectroscopy, and Keck/OSIRIS integral-field spectroscopy. We find a ~10 kpc cone of photoionized gas south of the galaxy center and a ~1 kpc semi-spherical front of shocked gas, which is responsible for the velocity offset in the emission lines, north of the galaxy center. We interpret these two outflows as the result of two separate AGN accretion events: the first AGN outburst created the southern outflow, and then \u3c105 later, the second AGN outburst launched the northern shock front. SDSS J1354+1327 is the galaxy with the strongest evidence for an AGN that has turned off and then on again, and it fits into the broader context of AGN flickering that includes observations of AGN light echoes