71 research outputs found
Metabolic Disposition of Phenylbutazone and Oxyphenbutazone in the horse
Imperial Users onl
Inflation from Geometrical Tachyons
We propose an alternative formulation of tachyon inflation using the
geometrical tachyon arising from the time dependent motion of a BPS -brane
in the background geometry due to parallel 5-branes arranged around a
ring of radius . Due to the fact that the mass of this geometrical tachyon
field is times smaller than the corresponding open-string tachyon
mass, we find that the slow roll conditions for inflation and the number of
e-foldings can be satisfied in a manner that is consistent with an effective
4-dimensional model and with a perturbative string coupling. We also show that
the metric perturbations produced at the end of inflation can be sufficiently
small and do not lead to the inconsistencies that plague the open string
tachyon models. Finally we argue for the existence of a minimum of the
geometrical tachyon potential which could give rise to a traditional reheating
mechanism.Comment: Latex, 20 pages, 4 figures; correction of algebraic errors in section
5 concerning the tachyon potential near its minimum. Conclusions unchange
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Geoscience/engineering characterization of the interwell environment in carbonate reservoirs based on outcrop analogs, Permian Basin, West Texas and New Mexico-stratigraphic hierarchy and cycle stacking facies distribution, and interwell-scale heterogeneity: Grayburg Formation, New Mexico. Final report
The Grayburg Formation (middle Guadalupian) is a major producing interval in the Permian Basin and has yielded more than 2.5 billion barrels of oil in West Texas. Grayburg reservoirs have produced, on average, less than 30 percent of their original oil in place and are undergoing secondary and tertiary recovery. Efficient design of such enhanced recovery programs dictates improved geological models to better understand and predict reservoir heterogeneity imposed by depositional and diagenetic controls. The Grayburg records mixed carbonate-siliciclastic sedimentation on shallow-water platforms that rimmed the Delaware and Midland Basins. Grayburg outcrops in the Guadalupe and Brokeoff Mountains region on the northwest margin of the Delaware Basin present an opportunity to construct a detailed, three-dimensional image of the stratigraphic and facies architecture. This model can be applied towards improved description and characterization of heterogeneity in analogous Grayburg reservoirs. Four orders of stratigraphic hierarchy are recognized in the Grayburg Formation. The Grayburg represents a long-term composite sequence composed of four high-frequency sequences (HFS 1-4). Each HFS contains several composite cycles comprising two or more cycles that define intermediate-scale transgressive-regressive successions. Cycles are the smallest scale upward-shoaling vertical facies successions that can be recognized and correlated across various facies tracts. Cycles thus form the basis for establishing the detailed chronostratigraphic correlations needed to delineate facies heterogeneity
Non-Abelian (p,q) Strings in the Warped Deformed Conifold
We calculate the tension of -strings in the warped deformed conifold
using the non-Abelian DBI action. In the large flux limit, we find exact
agreement with the recent expression obtained by Firouzjahi, Leblond and
Henry-Tye up to and including order terms if is also taken to be
large. Furthermore using the finite prescription for the symmetrised trace
operation we anticipate the most general expression for the tension valid for
any . We find that even in this instance, corrections to the tension
scale as which is not consistent with simple Casimir scaling.Comment: 18 pages, Latex, 1 figure; Added a discussion of the case when the
warp factor parameter and typos correcte
M-flation: Inflation From Matrix Valued Scalar Fields
We propose an inflationary scenario, M-flation, in which inflation is driven
by three hermitian matrices . The inflation
potential of our model, which is strongly motivated from string theory, is
constructed from and their commutators. We show that one can
consistently restrict the classical dynamics to a sector in which the
are proportional to the irreducible representations of SU(2). In
this sector our model effectively behaves as an N-flation model with
number of fields and the effective inflaton field has a super-Planckian field
value. Furthermore, the fine-tunings associated with unnaturally small
couplings in the chaotic type inflationary scenarios are removed. Due to the
matrix nature of the inflaton fields there are extra scalar fields in
the dynamics. These have the observational effects such as production of
iso-curvature perturbations on cosmic microwave background. Moreover, the
existence of these extra scalars provides us with a natural preheating
mechanism and exit from inflation. As the effective inflaton field can traverse
super-Planckian distances in the field space, the model is capable of producing
a considerable amount of gravity waves that can be probed by future CMB
polarization experiments such as PLANCK, QUIET and CMBPOL.Comment: minor changes, the counting of the alpha and beta modes are
corrected, references adde
On Power Law Inflation in DBI Models
Inflationary models in string theory which identify the inflaton with an open
string modulus lead to effective field theories with non-canonical kinetic
terms: Dirac-Born-Infeld scalar field theories. In the case of a -brane
moving in an AdS throat with a quadratic scalar field potential DBI kinetic
terms allow a novel realization of power law inflation. This note adresses the
question of whether this behaviour is special to this particular choice of
throat geometry and potential. The answer is that for any throat geometry one
can explicitly find a potential which leads to power law inflation. This
generalizes the well known fact that an exponential potential gives power law
inflation in the case of canonical kinetic terms.Comment: References and comments adde
Towards an Observational Appraisal of String Cosmology
We review the current observational status of string cosmology when
confronted with experimental datasets. We begin by defining common
observational parameters and discuss how they are determined for a given model.
Then we review the observable footprints of several string theoretic models,
discussing the significance of various potential signals. Throughout we comment
on present and future prospects of finding evidence for string theory in
cosmology, and on significant issues for the future.Comment: Review accepted for publication in the CQG focus issue on string
cosmology. Minor clarifications and references adde
Patient acceptability of home monitoring for neovascular age-related macular degeneration reactivation:a qualitative study
Neovascular age-related macular degeneration (nAMD) is a chronic, progressive condition and the commonest cause of visual disability in older adults. This study formed part of a diagnostic test accuracy study to quantify the ability of three index home monitoring (HM) tests (one paper-based and two digital tests) to identify reactivation in nAMD. The aim of this qualitative research was to investigate patients’ or participants’ views about acceptability and explore adherence to weekly HM. Semi-structured interviews were held with 78/297 participants (26%), with close family members (n = 11) and with healthcare professionals involved in training participants in HM procedures (n = 9) (n = 98 in total). A directed thematic analytical approach was applied to the data using a deductive and inductive coding framework informed by theories of technology acceptance. Five themes emerged related to: 1. The role of HM; 2. Suitability of procedures and instruments; 3. Experience of HM; 4. Feasibility of HM in usual practice; and 5. Impediments to patient acceptability of HM. Various factors influenced acceptability including a patient’s understanding about the purpose of monitoring. While initial training and ongoing support were regarded as essential for overcoming unfamiliarity with use of digital technology, patients viewed HM as relatively straightforward and non-burdensome. There is a need for further research about how use of performance feedback, level of support and nature of tailoring might facilitate further the implementation of routinely conducted HM. Home monitoring was acceptable to patients and they recognised its potential to reduce clinic visits during non-active treatment phases. Findings have implications for implementation of digital HM in the care of older people with nAMD and other long-term conditions
A Quintessentially Geometric Model
We consider string inspired cosmology on a solitary -brane moving in the
background of a ring of branes located on a circle of radius . The motion of
the -brane transverse to the plane of the ring gives rise to a radion field
which can be mapped to a massive non-BPS Born-Infeld type field with a cosh
potential. For certain bounds of the brane tension we find an inflationary
phase is possible, with the string scale relatively close to the Planck scale.
The relevant perturbations and spectral indices are all well within the
expected observational bounds. The evolution of the universe eventually comes
to be dominated by dark energy, which we show is a late time attractor of the
model. However we also find that the equation of state is time dependent, and
will lead to late time Quintessence.Comment: 11 pages, 3 figures. References and comments adde
Images of Embedded Jovian Planet Formation At A Wide Separation Around AB Aurigae
Direct images of protoplanets embedded in disks around infant stars provide
the key to understanding the formation of gas giant planets like Jupiter. Using
the Subaru Telescope and Hubble Space Telescope, we find evidence for a jovian
protoplanet around AB Aurigae orbiting at a wide projected separation (93 au),
likely responsible for multiple planet-induced features in the disk. Its
emission is reproducible as reprocessed radiation from an embedded protoplanet.
We also identify two structures located at 430-580 au that are candidate sites
of planet formation. These data reveal planet formation in the embedded phase
and a protoplanet discovery at wide, > 50 au separations characteristic of most
imaged exoplanets. With at least one clump-like protoplanet and multiple spiral
arms, the AB Aur system may also provide the evidence for a long-considered
alternative to the canonical model for Jupiter's formation: disk
(gravitational) instability.Comment: Author's personal version: 19 pages, 5 Figures, 1 Table; 32
Supplementary pages, 18 Supplementary Figures, 1 Supplementary Table;
Accepted for Publication in Nature Astronomy. Published version:
https://www.nature.com/articles/s41550-022-01634-
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