302 research outputs found
ExoMol molecular line lists - XVII The rotation-vibration spectrum of hot SO
Sulphur trioxide (SO) is a trace species in the atmospheres of the Earth
and Venus, as well as well as being an industrial product and an environmental
pollutant. A variational line list for SO, named UYT2, is
presented containing 21 billion vibration-rotation transitions. UYT2 can be
used to model infrared spectra of SO at wavelengths longwards of 2 m
( cm) for temperatures up to 800 K. Infrared absorption
cross sections are also recorded at 300 and 500 C are used to validate the UYT2
line list. The intensities in UYT2 are scaled to match the measured cross
sections. The line list is made available in electronic form as supplementary
data to this article and at \url{www.exomol.com}.Comment: 15 pages, 10 figures, 9 tables MNRAS submitte
ExoMol molecular line lists - XIV. The rotation-vibration spectrum of hot SO<sub>2</sub>
Sulphur dioxide is well-known in the atmospheres of planets and satellites,
where its presence is often associated with volcanism, and in circumstellar
envelopes of young and evolved stars as well as the interstellar medium. This
work presents a line list of 1.3 billion SO
vibration-rotation transitions computed using an empirically-adjusted potential
energy surface and an ab initio dipole moment surface. The list gives complete
coverage up to 8000 cm (wavelengths longer than 1.25 m) for
temperatures below 2000 K. Infrared absorption cross sections are recorded at
300 and 500 C are used to validated the resulting ExoAmes line list. The line
list is made available in electronic form as supplementary data to this article
and at www.exomol.com.Comment: Submitted to MNRA
Towards an Explicit Model of D-brane Inflation
We present a detailed analysis of an explicit model of warped D-brane
inflation, incorporating the effects of moduli stabilization. We consider the
potential for D3-brane motion in a warped conifold background that includes
fluxes and holomorphically-embedded D7-branes involved in moduli stabilization.
Although the D7-branes significantly modify the inflaton potential, they do not
correct the quadratic term in the potential, and hence do not cause a uniform
change in the slow-roll parameter eta. Nevertheless, we present a simple
example based on the Kuperstein embedding of D7-branes, z_1=constant, in which
the potential can be fine-tuned to be sufficiently flat for inflation. To
derive this result, it is essential to incorporate the fact that the
compactification volume changes slightly as the D3-brane moves. We stress that
the compactification geometry dictates certain relationships among the
parameters in the inflaton Lagrangian, and these microscopic constraints impose
severe restrictions on the space of possible models. We note that the shape of
the final inflaton potential differs from projections given in earlier studies:
in configurations where inflation occurs, it does so near an inflection point.
Finally, we comment on the difficulty of making precise cosmological
predictions in this scenario. This is the companion paper to arXiv:0705.3837.Comment: 68 pages, 6 figures; v2: fixed typos, added refs and clarifications;
v3: expanded discussion of inflection point inflatio
Cracking in asphalt materials
This chapter provides a comprehensive review of both laboratory characterization and modelling of bulk material fracture in asphalt mixtures. For the purpose of organization, this chapter is divided into a section on laboratory tests and a section on models. The laboratory characterization section is further subdivided on the basis of predominant loading conditions (monotonic vs. cyclic). The section on constitutive models is subdivided into two sections, the first one containing fracture mechanics based models for crack initiation and propagation that do not include material degradation due to cyclic loading conditions. The second section discusses phenomenological models that have been developed for crack growth through the use of dissipated energy and damage accumulation concepts. These latter models have the capability to simulate degradation of material capacity upon exceeding a threshold number of loading cycles.Peer ReviewedPostprint (author's final draft
Induction of fibroblast senescence generates a non-fibrogenic myofibroblast phenotype that differentially impacts on cancer prognosis
Cancer-associated fibroblasts (CAF) remain a poorly characterized, heterogeneous cell population. Here we characterized two previously described tumor-promoting CAF sub-types, smooth muscle actin (SMA)-positive myofibroblasts and senescent fibroblasts, identifying a novel link between the two. Analysis of CAF cultured ex vivo, showed that senescent CAF are predominantly SMA-positive; this was confirmed by immunochemistry in head & neck (HNSCC) and esophageal (EAC) cancers. In vitro, we found that fibroblasts induced to senesce develop molecular, ultrastructural and contractile features typical of myofibroblasts and this is dependent on canonical TGF-? signaling. Similar to TGF-?1-generated myofibroblasts, these cells secrete soluble factors that promote tumor cell motility. However, RNA-sequencing revealed significant transcriptomic differences between the two SMA-positive CAF groups, particularly in genes associated with extracellular matrix (ECM) deposition and organization, which differentially promote tumor cell invasion. Notably, second harmonic generation imaging and bioinformatic analysis of SMA-positive human HNSCC and EAC showed that collagen fiber organization correlates with poor prognosis, indicating that heterogeneity within the SMA-positive CAF population differentially impacts on survival. These results show that non-fibrogenic, SMA-positive myofibroblasts can be directly generated through induction of fibroblast senescence and suggest that senescence and myofibroblast differentiation are closely linked processes
Shaping gold nanocomposites with tunable optical properties
We report the synthesis of morphological uniform composites using miniemulsions of poly(tert-butyl acrylate) or
poly(styrene) containing organically capped gold nanocrystals (NCs). The optical features of such hybrid structures are
dominated by plasmonic effects and depend critically on the morphology of the resulting nanocomposite. In particular,
we demonstrate the ability to tune the overall optical response in the visible spectral region by varying the Au NCs
arrangement within the polymer matrix, and therefore the interparticle plasmon coupling, using Au NCs resulting from
the same batch of synthesis. This is a consequence of two well-known effects on the optical properties of Au particles: the
variation of the surrounding dielectric refractive index and interparticle plasmonic coupling. The research reported here
shows a general strategy to produce optical responsive nanocomposites via control of the morphology of submicrometric
polymer particles containing metal nanocrystals and thus is an alternative to the more common strategy of size
tuning metal nanoparticles used as nanofillers
Reduction in downstream test utilization following introduction of coronary computed tomography in a cardiology practice
To compare utilization of non-invasive ischemic testing, invasive coronary angiography (ICA), and percutaneous coronary intervention (PCI) procedures before and after introduction of 64-slice multi-detector row coronary computed tomographic angiography (CCTA) in a large urban primary and consultative cardiology practice. We utilized a review of electronic medical records (NotesMD®) and the electronic practice management system (Megawest®) encompassing a 4-year period from 2004 to 2007 to determine the number of exercise treadmill (TME), supine bicycle exercise echocardiography (SBE), single photon emission computed tomography (SPECT) myocardial perfusion stress imaging (MPI), coronary calcium score (CCS), CCTA, ICA, and PCI procedures performed annually. Test utilization in the 2 years prior to and 2 years following availability of CCTA were compared. Over the 4-year period reviewed, the annual utilization of ICA decreased 45% (2,083 procedures in 2004 vs. 1,150 procedures in 2007, P < 0.01) and the percentage of ICA cases requiring PCI increased (19% in 2004 vs. 28% in 2007, P < 0.001). SPECT MPI decreased 19% (3,223 in 2004 vs. 2,614 in 2007 P < 0.02) and exercise stress treadmill testing decreased 49% (471 in 2004 vs. 241 in 2007 P < 0.02). Over the same period, there were no significant changes in measures of practice volume (office and hospital) or the annual incidence of PCI (405 cases in 2004 vs. 326 cases in 2007) but a higher percentage of patients with significant disease undergoing PCI 19% in 2004 vs. 29% in 2007 P < 0.01. Implementation of CCTA resulted in a significant decrease in ICA and a corresponding significant increase in the percentage of ICA cases requiring PCI, indicating that CCTA resulted in more accurate referral for ICA. The reduction in unnecessary ICA is associated with avoidance of potential morbidity and mortality associated with invasive diagnostic testing, reduction of downstream SPECT MPI and TME as well as substantial savings in health care dollars
On Cosmological Constants from alpha'-Corrections
We examine to what extent perturbative alpha'-corrections can generate a
small cosmological constant in warped string compactifications. Focusing on the
heterotic string at lowest order in the string loop expansion, we show that,
for a maximally symmetric spacetime, the alpha'-corrected 4D scalar potential
has no effect on the cosmological constant. The only relevant terms are instead
higher order products of 4D Riemann tensors, which, however, are found to
vanish in the usual perturbative regime of the alpha'-expansion. The heterotic
string therefore only allows for 4D Minkowski vacua to all orders in alpha',
unless one also introduces string loop and/or nonperturbative corrections or
allows for curvatures or field strengths that are large in string units. In
particular, we find that perturbative alpha'-effects cannot induce weakly
curved AdS_4 solutions.Comment: 18 pages, no figures. v2: minor modifications, references adde
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