A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

Reshaping spatiality : cognitive perception and the fracturing of theatrical space

Drawing on the tenets of cognitive science, particularly Lakoff and Johnson's writing on metaphor, this thesis investigates the ways in which perception is constructed spatially by focusing on contemporary artists' engagement with rehearsal processes and performances where technology asserts control over the boundaries of space, centring specifically on the author's own practice. This interrogation of theatricality includes three practical research projects (performances) and a three-chapter written thesis that explores the theoretical and practical concerns of artistic engagement with an understanding of space. This thesis explores the physicality of experience via cognitive science and positions it within the realm of the artist, addressing the ways in which material practitioners are always engaged in the experience of materiality. In both the written and practical components of this thesis, I interrogate and propose that space is perceived and constructed not only physically but also experientially. One of the key methodologies of this thesis is to locate, articulate and reflect upon the complex interaction between writing and practice: how material practice affects discourse and vice versa. Chapter One investigates heads pace, which is a feature of performance work that takes place largely in the head of an audience member, by using a set of techniques and technologies that subvert physical space - often including headphones worn by audience members. This chapter introduces many of the arguments of the larger thesis and establishes headspace as a viable term by reviewing the neurology of hearing and contemporary writing on sound reception, and through a dissection of four practical works, one of which was created by the author prior to this thesis: Whisper (Petralia, 2007), The Telephone Call (Cardiff, 2001), The Missing Voice (Cardiff, 1999) and Desire Paths (spell#7, 2004). Chapter Two concerns itself with aberrant pixel space, which, in the context of this project, is concerned with the internal architecture of the screen in relation to the external architecture of the stage in performance. Specifically, aberrant pixel space considers performances that use a cinematic and/or televisual frame that creates distinctions between what is in the shot, and what is not, uses the editing techniques of cinema/television, and plays with scale through its use of fragmented live performance and , perfect screen imagery. Aberrant pixel space is explored through the creation of a practice- as research performance work titled Virtuoso (working title) (petralia, 2009), which uses screens that form the boundaries of a space whose logic is defined by the properties of the television landscape. The work of Big Art Group and Gregory Crewdson are positioned alongside Virtuoso (working title) to understand the characteristics of spaces that can be understood via the extended metaphor of the pixel. Chapter Three focuses on telematic rehearsal space, which suggests that processes of artistic creation are not fixed to specific geographical locations but are in fact transitory, existing in the interchange between physical space and the space of communication. Chapter Three specifically considers the use of videoconferencing in rehearsal processes, using three performances including two new pieces created by the author in collaboration with Tiffany Mills Company: the dance- theatre works Tomorrow's Legs and Berries and Bulls, along with the work of other artists including Mabou Mines. The thesis concludes by interrogating the ways in which these three distinct spaces relate, reflecting on the ways in which space is contingent upon experience. Further, the conclusion discusses the ways that this thesis contributes to a new approach for understanding the making and witnessing process of live performance.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Whisper

Whisper is a visually decadent, aurally immersive performance that asks the audience to question ‘what is real’ in a world of increasing technological sophistication. Each audience member is given a set of headphones through which they hear the voices of three live performers narrating a fictional walk through a fictional city. Obscured behind a cinematic screen, the performers are seen as shadows, silhouettes or in stark clarity, creating a fully immersive sound environment to accompany their narration. Not only are the three performers narrating a walk that switches between the ‘here and now’ of the story and ‘dream-world’ of memory, but they are also creating a fully immersive sound environment through the use of a sound technique called foley. Foley is a technique employed in film, where a sound artist adds sounds to a film after the film has been shot, thereby creating a hyper-realistic world of sound for the film

Selective loss of NMDA receptor NR1 subunit isoforms in Alzheimer's disease

Previous work had shown that the ratio of NMDA receptor NR1 subunit mRNA transcripts containing an N-terminal splice cassette to those that do not is markedly lower in regions of the Alzheimer's disease (AD) brain that are susceptible to pathological damage, compared with spared regions in the same cases or homotropic regions in controls. To elucidate the origins of this difference in proportionate expression, we measured the absolute levels of each of the eight NR1 transcripts by quantitative internally standardized RT-PCR assay. Expression of transcripts with the cassette was strongly attenuated in susceptible regions of Alzheimer's brain, whereas expression of non-cassette transcripts differed little from that in controls. The expression of other NR1 splice variants was not associated with pathology relevant to disease status, although some combinations of splice cassettes were well maintained in AD cases. The population profile of NR1 transcripts in occipital cortex differed from the profiles in other brain regions studied. Western analysis confirmed that the expression of protein isoforms containing the N-terminal peptide was very low in susceptible areas of the Alzheimer's brain. Cells that express NR1 subunits with the N-terminal cassette may be selectively vulnerable to toxicity in AD

The role of group I metabotropic glutamate receptor's in neuronal excitotoxicity in Alzheimer's disease

Neurodegenerative diseases such as Huntington's disease, ischemia, and Alzheimer's disease (AD) are major causes of death. Recently, metabotropic glutamate receptors (mGluRs), a group of seven-transmembrane-domain proteins that couple to G-proteins, have become of interest for studies of pathogenesis. Group I mGluRs control the levels of second messengers such as inositol 1,4,5-triphosphate (IP3) Cal(2+) ions and cAMP. They elicit the release of arachidonic acid via intracellular Ca2+ mobilization from intracellular stores such as mitochondria and endoplasmic reticulum. This facilitates the release of glutamate and could trigger the formation of neurofibrillary tangles, a pathological hallmark of AD. mGluRs regulate neuronal injury and survival, possibly through a series of downstream protein kinase and cysteine protease signaling pathways that affect mitochondrially mediated programmed cell death. They may also play a role in glutamate-induced neuronal death by facilitating Cal(2+) mobilization. Hence, mGluRs have become a target for neuroprotective drug development. They represent a pharmacological path to a relatively subtle amelioration of neurotoxicity because they serve a modulatory rather than a direct role in excitatory glutamatergic transmission