1,630 research outputs found
Self/portrait
SELF/PORTRAIT is an exploration of the creative process. Based in the genre of portraiture, this collection of work seeks to reveal the ways in which the artist's relationships and circumstances have factored into the creation of the resulting exhibition. This exploration involves the assessment of abandoned projects with the aim of gaining a greater understanding of their qualities that have served to motivate the creation of his art, and those that have hindered his artistic process. This thesis exhibition and support paper use an autobiographical approach to seek the elements of the artist's perception of art which have influenced the production of the work displayed, and how these are effected by the task of creating a Master's thesis exhibition. It explores the qualities of both Portraiture and Painting which have inspired and directed his endeavour. SELF/PORTRAIT seeks to display the artist's work as a process rather than a product
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Twisted Tales: Insights into Genome Diversity of Ciliates Using Single-Cell 'Omics.
The emergence of robust single-cell 'omics techniques enables studies of uncultivable species, allowing for the (re)discovery of diverse genomic features. In this study, we combine single-cell genomics and transcriptomics to explore genome evolution in ciliates (a > 1 Gy old clade). Analysis of the data resulting from these single-cell 'omics approaches show: 1) the description of the ciliates in the class Karyorelictea as "primitive" is inaccurate because their somatic macronuclei contain loci of varying copy number (i.e., they have been processed by genome rearrangements from the zygotic nucleus); 2) gene-sized somatic chromosomes exist in the class Litostomatea, consistent with Balbiani's (1890) observation of giant chromosomes in this lineage; and 3) gene scrambling exists in the underexplored Postciliodesmatophora (the classes Heterotrichea and Karyorelictea, abbreviated here as the Po-clade), one of two major clades of ciliates. Together these data highlight the complex evolutionary patterns underlying germline genome architectures in ciliates and provide a basis for further exploration of principles of genome evolution in diverse microbial lineages
New symmetry current for massive spin-3/2 fields
We present several new results which will be of value to theorists working
with massive spin-3/2 vector-spinor fields as found, for example, in low and
intermediate energy hadron physics and also linearized supergravity. The
general lagrangian and propagator for a vector-spinor field in d-dimensions is
given. It is shown that the observables of the theory are invariant under a
novel continuous symmetry group which is also extended to an algebra. A new
technique is developed for exploring the consequences of the symmetry and a
previously unknown conserved vector current and charge are found. The current
leads to new interactions involving spin-3/2 particles and may have important
experimental consequences.Comment: 9 pages, references updated and minor change
Dissociation of the benzene molecule by UV and soft X-rays in circumstellar environment
Benzene molecules, present in the proto-planetary nebula CRL 618, are ionized
and dissociated by UV and X-ray photons originated from the hot central star
and by its fast wind. Ionic species and free radicals produced by these
processes can lead to the formation of new organic molecules. The aim of this
work is to study the photoionization and photodissociation processes of the
benzene molecule, using synchrotron radiation and time of flight mass
spectrometry. Mass spectra were recorded at different energies corresponding to
the vacuum ultraviolet (21.21 eV) and soft X-ray (282-310 eV) spectral regions.
The production of ions from the benzene dissociative photoionization is here
quantified, indicating that C6H6 is more efficiently fragmented by soft X-ray
than UV radiation, where 50% of the ionized benzene molecules survive to UV
dissociation while only about 4% resist to X-rays. Partial ion yields of H+ and
small hydrocarbons such as C2H2+, C3H3+ and C4H2+ are determined as a function
of photon energy. Absolute photoionization and dissociative photoionization
cross sections have also been determined. From these values, half-life of
benzene molecule due to UV and X-ray photon fluxes in CRL 618 were obtained.Comment: The paper contains 8 pages, 9 figures and 4 tables. Accepted to be
published on MNRAS on 2008 November 2
Communications: Mechanical Deformation of Dendrites by Fluid Flow
It is generally accepted that liquid agitation during alloy solidification assists in crystal multiplication, as in dendrite fragmentation and the detachment of side arms in the mushy region of a casting. Even without deliberate stirring by electromagnetic or mechanical means, there is often vigorous interdendritic fluid flow promoted by natural thermosolutal convection. In this analysis, we shall estimate the stress at the root of a secondary dendrite arm of aluminum arising from the action of a flow of molten metal past the dendrite arm
Radiolysis of ammonia-containing ices by energetic, heavy and highly charged ions inside dense astrophysical environments
Deeply inside dense molecular clouds and protostellar disks, the interstellar
ices are protected from stellar energetic UV photons. However, X-rays and
energetic cosmic rays can penetrate inside these regions triggering chemical
reactions, molecular dissociation and evaporation processes. We present
experimental studies on the interaction of heavy, highly charged and energetic
ions (46 MeV Ni^13+) with ammonia-containing ices in an attempt to simulate the
physical chemistry induced by heavy ion cosmic rays inside dense astrophysical
environments. The measurements were performed inside a high vacuum chamber
coupled to the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions
Lourds) in Caen, France.\textit{In-situ} analysis is performed by a Fourier
transform infrared spectrometer (FTIR) at different fluences. The averaged
values for the dissociation cross section of water, ammonia and carbon monoxide
due to heavy cosmic ray ion analogs are ~2x10^{-13}, 1.4x10^{-13} and
1.9x10^{-13} cm, respectively. In the presence of a typical heavy cosmic
ray field, the estimated half life for the studied species is 2-3x10^6 years.
The ice compaction (micropore collapse) due to heavy cosmic rays seems to be at
least 3 orders of magnitude higher than the one promoted by (0.8 MeV) protons .
In the case of the irradiated H2O:NH3:CO ice, the infrared spectrum at room
temperature reveals five bands that were tentatively assigned to vibration
modes of the zwitterionic glycine (+NH3CH2COO-).Comment: Accepted to be published in Astronomy and Astrophysics; Number of
pages: 12; Number of Figures: 7; Number of Tables:
Characterization of acetonitrile ice irradiated by X-rays employing the PROCODA code: II. Desorption processes
In this work, we focus on the study of radiation induced desorption processes
that occurred in acetonitrile ice irradiated by broadband X-rays (6 eV to 2
keV) monitored by FTIR spectroscopy at different radiation fluences. In a
previous work, we used the PROCODA code to derive the chemical evolution of the
ice. Here, we have obtained that the acetonitrile desorbed column density is at
least two orders of magnitude larger than the desorbed column densities of
daughter or granddaughter molecular species at chemical equilibrium stage. This
indicates that total desorption column density is mainly governed by the father
molecule, as also previously hypothesized in experimental studies. This occurs
basically because the acetonitrile column density is larger than the other
ones. In particular, at chemical equilibrium acetonitrile desorption column
density represents almost 98\% of the total, while it is close to 1\% for H, CN
and CH, the species with larger molecular desorption percentages at
chemical equilibrium. Another derived quantity is what we called intrinsic
desorption rate, which is a number per second for individual species. Some of
the larger intrinsic desorption rates were: CHCN (), CN
(), H (), CH ()
and CN (). These results help to put constrain in
astrochemical models and can be also useful to clarify some astronomical radio
observations.Comment: To appear in MNRA
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