556 research outputs found
Photon and Z induced heavy charged lepton pair production at a hadron supercollider
We investigate the pair production of charged heavy leptons via
photon-induced processes at the proposed CERN Large Hadron Collider (LHC).
Using effective photon and Z approximations, rates are given for
production due to fusion and fusion for the cases of
inelastic, elastic and semi-elastic collisions. These are compared with
the corresponding rates for production via the gluon fusion and Drell-Yan
mechanisms. Various and differential luminosities
for collisions are also presented.Comment: 22 pages, RevTex 3.0, 6 uuencoded and compressed postscript figures
included. Reference to one paper changed from the original preprint number to
the published version. Everything else unchange
Recursive Calculation of One-Loop QCD Integral Coefficients
We present a new procedure using on-shell recursion to determine coefficients
of integral functions appearing in one-loop scattering amplitudes of gauge
theories, including QCD. With this procedure, coefficients of integrals,
including bubbles and triangles, can be determined without resorting to
integration. We give criteria for avoiding spurious singularities and boundary
terms that would invalidate the recursion. As an example where the criteria are
satisfied, we obtain all cut-constructible contributions to the one-loop
n-gluon scattering amplitude, A_n^{oneloop}(...--+++...), with split-helicity
from an N=1 chiral multiplet and from a complex scalar. Using the
supersymmetric decomposition, these are ingredients in the construction of QCD
amplitudes with the same helicities. This method requires prior knowledge of
amplitudes with sufficiently large numbers of legs as input. In many cases,
these are already known in compact forms from the unitarity method.Comment: 36 pages; v2 clarification added and typos fixed, v3 typos fixe
Effects of small surface tension in Hele-Shaw multifinger dynamics: an analytical and numerical study
We study the singular effects of vanishingly small surface tension on the
dynamics of finger competition in the Saffman-Taylor problem, using the
asymptotic techniques described in [S. Tanveer, Phil. Trans. R. Soc. Lond. A
343, 155 (1993)]and [M. Siegel, and S. Tanveer, Phys. Rev. Lett. 76, 419
(1996)] as well as direct numerical computation, following the numerical scheme
of [T. Hou, J. Lowengrub, and M. Shelley,J. Comp. Phys. 114, 312 (1994)]. We
demonstrate the dramatic effects of small surface tension on the late time
evolution of two-finger configurations with respect to exact (non-singular)
zero surface tension solutions. The effect is present even when the relevant
zero surface tension solution has asymptotic behavior consistent with selection
theory.Such singular effects therefore cannot be traced back to steady state
selection theory, and imply a drastic global change in the structure of
phase-space flow. They can be interpreted in the framework of a recently
introduced dynamical solvability scenario according to which surface tension
unfolds the structually unstable flow, restoring the hyperbolicity of
multifinger fixed points.Comment: 16 pages, 15 figures, submitted to Phys. Rev
A combined geochemical and μCT study on the CO2 reactivity of Surat Basin reservoir and cap-rock cores: porosity changes, mineral dissolution and fines migration
Geological storage of CO generally involves injection of a CO stream into a high porosity and permeability reservoir, contained by one or more overlying low permeability formations. Sandstone reservoirs and associated cap-rocks of targeted CO storage sites therefore have distinct properties such as porosity and mineral contents. Their geochemical response or reactivity to injected supercritical CO and associated changes in porosity, and permeability affecting scaling, mineral trapping, injectivity, or migration can therefore be very different. Six drill core samples including quartz-rich sandstones, calcite cemented sandstones, and feldspar or clay-rich cap-rocks from a proposed demonstration site in the Surat Basin, Australia, were characterized before and after reaction with pure supercritical CO and low salinity formation water. The quartz-rich sandstones have low reactivity, and maintain high porosities with visible pore connectivity after reaction, they are unlikely to be affected by scaling. Kaolin and fine grain movement observed via μCT and SEM could have the potential to open or plug pores, potentially increasing or decreasing permeability and CO injectivity. Calcite cemented sandstones had the greatest measured change in porosity after reaction via calcite dissolution. Narrow angular channels were formed in the calcite cement around framework grains, extending through to the center of the sub-plug in the courser grained rock, and surface roughness increased. Solution pH was however quickly passivated. The highest concentrations of Ca, Mn, Sr, and Mg were released to solution from calcite dissolution. Clay (and feldspar) rich cap-rock core had mainly microporosity and the smallest initial pore throat diameters associated with clays. Small changes to μCT calculated porosities after reaction were related to a decrease in chlorite X-ray density, and dissolution of patchy carbonate minerals. Pores were disconnected in μCT images, except for some created horizontal connection along a sandy lamination in a cap-rock. Dissolved concentrations of Ca, Fe, Si, Sr, Mn, Li and Mg increased via dissolution of both carbonate and silicate minerals. Dissolved Ca, Fe, Mn and Mg from silicate minerals in the cap-rock were available for longer term mineral trapping of CO. Potential increases in porosity and migration will be highest in the calcite cemented zones, while clay-rich cap-rocks could be expected to maintain integrity. There is a low likelihood of mineral trapping or scaling in the quartz rich lower Precipice Sandstone. Overlying rocks can provide Fe, Mg, Ca for mineral trapping of CO as ferroan carbonates such as siderite, ankerite and dolomite over longer time scales when pH is buffered. Changes to porosity, mineral content, and water chemistry after pure CO reaction observed here and in other published studies were dependent on mineral content and fluid accessibility. These results could be generalized to other sandstone reservoirs where it is expected to inject CO. The results can also be used to validate geochemical models to build longer term predictions
Next-to-leading order jet distributions for Higgs boson production via weak-boson fusion
The weak-boson fusion process is expected to provide crucial information on
Higgs boson couplings at the Large Hadron Collider at CERN. The achievable
statistical accuracy demands comparison with next-to-leading order QCD
calculations, which are presented here in the form of a fully flexible parton
Monte Carlo program. QCD corrections are determined for jet distributions and
are shown to be modest, of order 5 to 10% in most cases, but reaching 30%
occasionally. Remaining scale uncertainties range from order 5% or less for
distributions to below +-2% for the Higgs boson cross section in typical
weak-boson fusion search regions.Comment: 19 pages, 8 figure
Ligneous membranitis in Scottish terriers is associated with a single nucleotide polymorphism in the plasminogen (plg) gene
Ligneous membranitis (LM) is a rare chronic inflammatory condition of the mucous membranes associated with plasminogen (encoded by PLG) deficiency in affected humans and dogs. In human, the condition is genetic in nature with numerous mutations and polymorphisms in PLG identified in affected individuals and related family members. The condition is uncommonly reported in dogs and, to date, no genetic studies have been performed. We identified related Scottish Terriers (littermates) with severe LM and unaffected relatives (sire, dam and a sibling from a previous litter). Plasma plasminogen activity was below normal in one affected dog but within normal reference intervals for the other. Sequencing of PLG from the affected dogs revealed a homozygous A>T single nucleotide polymorphism in an intron donor site (c.1256+2T>A). The related, unaffected dogs displayed heterozygous alleles at this position (c.1256+2T/A), whereas no mutation was detected in unaffected, non‐related control dogs. This is the first report to identify gene polymorphisms associated with LM in dogs
Great Artesian Basin authigenic carbonates as natural analogues for mineralisation trapping
This project is the first to comprehensively investigate the controls on the formation of authigenic carbonates in low salinity, siliciclastic aquifers of the Great Artesian Basin. These processes are\ua0natural analogues for mineralisation trapping of CO2 during geo-sequestration. Calcite is the main carbonate present. Analyses included elemental composition, C and O stable isotopes, fluid inclusion analyses including\ua0gas isotopes, SEM-EDS and QEMSCAN, and X-ray micro-CT scanning.\ua0The samples reflect\ua0a variety of fluid origins, compositions, and temperatures of precipitation.\ua0Differentiating between carbonate formed via different mechanisms, and determining controls on the extent of authigenic carbonate formation, could lead to options for engineered accelerated mineralisation in reservoirs
Dynamical Systems approach to Saffman-Taylor fingering. A Dynamical Solvability Scenario
A dynamical systems approach to competition of Saffman-Taylor fingers in a
channel is developed. This is based on the global study of the phase space
structure of the low-dimensional ODE's defined by the classes of exact
solutions of the problem without surface tension. Some simple examples are
studied in detail, and general proofs concerning properties of fixed points and
existence of finite-time singularities for broad classes of solutions are
given. The existence of a continuum of multifinger fixed points and its
dynamical implications are discussed. The main conclusion is that exact
zero-surface tension solutions taken in a global sense as families of
trajectories in phase space spanning a sufficiently large set of initial
conditions, are unphysical because the multifinger fixed points are
nonhyperbolic, and an unfolding of them does not exist within the same class of
solutions. Hyperbolicity (saddle-point structure) of the multifinger fixed
points is argued to be essential to the physically correct qualitative
description of finger competition. The restoring of hyperbolicity by surface
tension is discussed as the key point for a generic Dynamical Solvability
Scenario which is proposed for a general context of interfacial pattern
selection.Comment: 3 figures added, major rewriting of some sections, submitted to Phys.
Rev.
Comparing research priority-setting partnerships for older adults across international health care systems: a systematic review
OBJECTIVES: Priority setting partnerships (PSPs) attempt to shape the research agenda to address the needs of local populations of interest. We reviewed the PSPs for older adults, with a focus on exemplar health care systems: United Kingdom (UK; publicly funded), United States (private health insurance-based), South Korea (national health insurance-based), and Africa (out-of-pocket). DESIGN: Systematic review. SETTING AND PARTICIPANTS: We searched databases and sources (January 2011-October 202l; updated in February 2023) for PSPs of older adults' health care. METHODS: Based on the British geriatric medicine curriculum, we extracted and categorized the PSP topics by areas and the research priorities by themes, and generated evidence maps depicting and comparing the research gaps across the systems. We evaluated PSP quality using the Nine Common Themes of Good Clinical Practice. RESULTS: We included 32 PSPs (United Kingdom: n = 25; United States: n = 7; South Korea and Africa: n = 0) and identified priorities regarding 27 conditions or service arrangements in the United Kingdom and 9 in the United States (predominantly in neurology/psychiatry). The UK priorities focused on treatments and interventions whereas the US on prognostic/predictive factors. There were notable research gaps within the existing PSPs, including common geriatric conditions like continence and frailty. The PSP quality evaluation revealed issues around lacking inclusion of ethnic minorities. CONCLUSIONS AND IMPLICATIONS: Research priorities for older adult health care vary internationally, but certain health care systems/countries have no available PSPs. Where PSPs are available, fundamental aspects of geriatric medicine have not been included. Future researchers should conduct prioritizations in different countries, focus on core geriatric syndromes, and ensure the inclusion of all relevant stakeholder groups
IL-33 activates tumor stroma to promote intestinal polyposis
Tumor epithelial cells develop within a microenvironment consisting of extracellular matrix, growth factors, and cytokines produced by nonepithelial stromal cells. In response to paracrine signals from tumor epithelia, stromal cells modify the microenvironment to promote tumor growth and metastasis. Here, we identify interleukin 33 (IL-33) as a regulator of tumor stromal cell activation and mediator of intestinal polyposis. In human colorectal cancer, IL-33 expression was induced in the tumor epithelium of adenomas and carcinomas, and expression of the IL-33 receptor, IL1RL1 (also referred to as IL1-R4 or ST2), localized predominantly to the stroma of adenoma and both the stroma and epithelium of carcinoma. Genetic and antibody abrogation of responsiveness to IL-33 in the ApcMin/+ mouse model of intestinal tumorigenesis inhibited proliferation, induced apoptosis, and suppressed angiogenesis in adenomatous polyps, which reduced both tumor number and size. Similar to human adenomas, IL-33 expression localized to tumor epithelial cells and expression of IL1RL1 associated with two stromal cell types, subepithelial myofibroblasts and mast cells, in ApcMin/+ polyps. In vitro, IL-33 stimulation of human subepithelial myofibroblasts induced the expression of extracellular matrix components and growth factors associated with intestinal tumor progression. IL-33 deficiency reduced mast cell accumulation in ApcMin/+ polyps and suppressed the expression of mast cell-derived proteases and cytokines known to promote polyposis. Based on these findings, we propose that IL-33 derived from the tumor epithelium promotes polyposis through the coordinated activation of stromal cells and the formation of a protumorigenic microenvironment
- …