1,038 research outputs found
Endovascular exclusion of iliac artery to iliac vein fistula after lumbar disk surgery
AbstractIliac arteriovenous (AV) fistula is rare after lumbar disk surgery. Traditionally, open repair through the arterial lumen was performed. We report endovascular exclusion of an iliac AV fistula in a 41-year-old woman 8 years after lumbar diskectomy. An angiogram showed an AV fistula connecting the right common iliac artery and vein. This was repaired with placement of two covered wall stents in the right common artery and external iliac artery, and embolization of the right internal iliac artery. Contrast medium-enhanced computed tomography scan at 5 months confirmed elimination of the AV fistula and right iliac artery patency. This technique should be considered in management of iliac AV fistulas. (J Vasc Surg 2003;37:1091-3.
Critical Behavior of a Three-State Potts Model on a Voronoi Lattice
We use the single-histogram technique to study the critical behavior of the
three-state Potts model on a (random) Voronoi-Delaunay lattice with size
ranging from 250 to 8000 sites. We consider the effect of an exponential decay
of the interactions with the distance,, with , and
observe that this system seems to have critical exponents and
which are different from the respective exponents of the three-state Potts
model on a regular square lattice. However, the ratio remains
essentially the same. We find numerical evidences (although not conclusive, due
to the small range of system size) that the specific heat on this random system
behaves as a power-law for and as a logarithmic divergence for
and Comment: 3 pages, 5 figure
Safety, tolerability and efficacy of intradermal rabies immunization with DebioJect™.
In a single-center study, 66 healthy volunteers aged between 18 and 50years were randomized to be immunized against rabies with three different injection routes: intradermal with DebioJect™ (IDJ), standard intradermal with classical needle (IDS), also called Mantoux method, and intramuscular with classical needle (IM). "Vaccin rabique Pasteur®" and saline solution (NaCl 0.9%) were administered at D0, D7 and D28. Antigen doses for both intradermal routes were 1/5 of the dose for IM. Tolerability, safety and induced immunogenicity of IDJ were compared to IDS and IM routes. Pain was evaluated at needle insertion and at product injection for all vaccination visits. Solicited Adverse Event (SolAE) and local reactogenicity symptoms including pain, redness and pruritus were recorded daily following each vaccination visit. Adverse events (AE) were recorded over the whole duration of the study. Humoral immune response was measured by assessing the rabies virus neutralizing antibody (VNA) titers using Rapid Fluorescent Focus Inhibition Test (RFFIT). Results demonstrated that the DebioJect™ is a safe, reliable and efficient device. Significant decreases of pain at needle insertion and at vaccine injection were reported with IDJ compared to IDS and IM. All local reactogenicity symptoms (pain, redness and pruritus) after injection with either vaccine or saline solution, were similar for IDJ and IDS, except that IDJ injection induced more redness 30min after saline solution. No systemic SolAE was deemed related to DebioJect™ and classical needles. No AE was deemed related to DebioJect™. No Serious Adverse Event (SAE) was reported during the study. At the end of the study all participants were considered immunized against rabies and no significant difference in humoral response was observed between the 3 studied routes
Effects of old landfills on groundwater quality. Phase 2, investigation of the Thriplow landfill 1996–1997
Disused sand and gravel excavations overlying the major Chalk aquifer at Thriplow in Cambridgeshire have
been filled with domestic waste in two phases. One area (Phase 1) was filled between 1957–77 with little compaction
of the refuse and was left uncapped, while Phase 2 was deposited between 1981–87 and capped with
clay. Aerial photography and surface resistivity surveys indicate that the site geometry is complex, with several
phases of landfilling into excavations of differing depths. Drilling through the waste indicates that leachate production
and waste stabilisation proceed at different rates in capped and uncapped landfills. Analysis of leachate
obtained by centrifugation or squeezing appears to give more insight into the pollution potential than do leach
tests with distilled water. The Biological Methane Potential (BMP) of the waste appears to be related to the
quantity of decomposable material but the chemical oxygen demand (COD) values are distorted by the presence
of reduced metals. Too few boreholes have been drilled to define the leachate source in terms of its spatial distribution
and little is known of how its composition has changed with time. However, hydraulic conductivity measurements
on the landfill caps suggest that it is sufficiently permeable for all rainfall to potentially infiltrate the
waste.
Boreholes outside the landfill penetrate the Upper and Lower Chalk, and identify the Melbourn Rock and underlying
Plenus Marls at the junction of the two formations about 20 m below ground level (bgl). Surface resistivity
surveys using the BGS RESCAN system, confirm aerial photographs of the extent of the landfill and also
suggest that leachate has migrated beyond the base of the landfill. Evidence of leachate migration in pre-existing
screened boreholes completed above and below the Plenus Marls suggests that leachate is flowing above the
Plenus Marls. Hydraulic head measurements whilst drilling a borehole to the base of the lower Chalk approx. 70
m bgl revealed the potential for upward groundwater flow through the Plenus Marls. Thus, previously-drilled
boreholes penetrating the Plenus Marls are expected to recharge upwards into the shallow aquifer above the
Plenus Marls diluting any leachate in the upper aquifer and distorting the flow regime. Several of these boreholes
have subsequently been modified to stem the flow across the Plenus Marls.
One borehole down-gradient to the west of the site revealed a large thickness of drift composed of both sand and
clay rich material. This suggests the existence of a buried channel, the hydrogeological significance of which has
yet to be assessed.
Groundwater chemistry appears to be influenced by three major factors. (a) the landfill leachate (b) the composition
of shallow groundwater in the top 10 m of the Chalk, and (c) the composition of water from the Lower
Chalk. Limited groundwater monitoring data appear to display a cyclic variation in chloride concentration. The
origin for this is not clear but it may correlate with cyclic variations in groundwater levels when the water table
rises into the waste. Cyclic flushing of the landfill may release leachate into the aquifer giving rise to pulses of
chloride. Alternatively changes in chloride may arise by the changing direction of groundwater flow which as yet
has not been assessed.
A conceptual hydrogeological model in which flow is limited to above the Plenus Marls has been used to
develop a more appropriate groundwater flow and solute transport model. However, the model lacks data on
aquifer properties, on contaminant inputs concentrations, fluxes and spatial variations, and there is a paucity of
monitoring data for calibration. Nonetheless preliminary transport modelling using an equivalent porous medium
approach shows that an effective porosity of about 5% best fits the regional data. Since this is much less than the
total porosity of about 40% for the Chalk, it would appear that only part of the Chalk is available for flow but
that matrix diffusion could play an important role in leachate attenuation. Discrete fracture modelling using the
FRACTRAN code has allowed some scoping to be made of the hydraulic properties of the aquifer by comparison
with chloride hydrographs, but these again need to be better conditioned by in-situ measurement of fracture
distributions and transmissivities.
A number of additional activities are required to improve the understanding of flow and contaminant transport at
the site. These include better spatial definition of the waste distribution, improved data on the hydraulic properties
of the Chalk aquifer, and the use of automatic monitoring to record temporal changes in groundwater chemistry
and groundwater levels
Stability and renormalization of Yang-Mills theory with Background Field Method: a regularization independent proof
In this paper the stability and the renormalizability of Yang-Mills theory in
the Background Field Gauge are studied. By means of Ward Identities of
Background gauge invariance and Slavnov-Taylor Identities the stability of the
classical model is proved and, in a regularization independent way, its
renormalizability is verified. A prescription on how to build the counterterms
is given and the possible anomalies which may appear for Ward Identities and
for Slavnov-Taylor Identities are shown.Comment: 25 pages, Latex 2.09, no figure
The Two-Loop Pinch Technique in the Electroweak Sector
The generalization of the two-loop Pinch Technique to the Electroweak Sector
of the Standard Model is presented. We restrict ourselves to the case of
conserved external currents, and provide a detailed analysis of both the
charged and neutral sectors. The crucial ingredient for this construction is
the identification of the parts discarded during the pinching procedure with
well-defined contributions to the Slavnov-Taylor identity satisfied by the
off-shell one-loop gauge-boson vertices; the latter are nested inside the
conventional two-loop self-energies. It is shown by resorting to a set of
powerful identities that the two-loop effective Pinch Technique self-energies
coincide with the corresponding ones computed in the Background Feynman gauge.
The aforementioned identities are derived in the context of the
Batalin-Vilkovisky formalism, a fact which enables the individual treatment of
the self-energies of the photon and the -boson. Some possible
phenomenological applications are briefly discussed.Comment: 50 pages, uses axodra
Citrullinated human and murine MOG<sub>35–55</sub> display distinct biophysical and biochemical behavior
The peptide spanning residues 35 to 55 of the protein myelin oligodendrocyte glycoprotein (MOG) has been studied extensively in its role as a key autoantigen in the neuroinflammatory autoimmune disease multiple sclerosis. Rodents and nonhuman primate species immunized with this peptide develop a neuroinflammatory condition called experimental autoimmune encephalomyelitis, often used as a model for multiple sclerosis. Over the last decade, the role of citrullination of this antigen in the disease onset and progression has come under increased scrutiny. We recently reported on the ability of these citrullinated MOG35–55 peptides to aggregate in an amyloid-like fashion, suggesting a new potential pathogenic mechanism underlying this disease. The immunodominant region of MOG is highly conserved between species, with the only difference between the murine and human protein, a polymorphism on position 42, which is serine in mice and proline for humans. Here, we show that the biophysical and biochemical behavior we previously observed for citrullinated murine MOG35–55 is fundamentally different for human and mouse MOG35–55. The citrullinated human peptides do not show amyloid-like behavior under the conditions where the murine peptides do. Moreover, we tested the ability of these peptides to stimulate lymphocytes derived from MOG immunized marmoset monkeys. While the citrullinated murine peptides did not produce a proliferative response, one of the citrullinated human peptides did. We postulate that this unexpected difference is caused by disparate antigen processing. Taken together, our results suggest that further study on the role of citrullination in MOG-induced experimental autoimmune encephalomyelitis is necessary.</p
Pinch Technique and the Batalin-Vilkovisky formalism
In this paper we take the first step towards a non-diagrammatic formulation
of the Pinch Technique. In particular we proceed into a systematic
identification of the parts of the one-loop and two-loop Feynman diagrams that
are exchanged during the pinching process in terms of unphysical ghost Green's
functions; the latter appear in the standard Slavnov-Taylor identity satisfied
by the tree-level and one-loop three-gluon vertex. This identification allows
for the consistent generalization of the intrinsic pinch technique to two
loops, through the collective treatment of entire sets of diagrams, instead of
the laborious algebraic manipulation of individual graphs, and sets up the
stage for the generalization of the method to all orders. We show that the task
of comparing the effective Green's functions obtained by the Pinch Technique
with those computed in the background field method Feynman gauge is
significantly facilitated when employing the powerful quantization framework of
Batalin and Vilkovisky. This formalism allows for the derivation of a set of
useful non-linear identities, which express the Background Field Method Green's
functions in terms of the conventional (quantum) ones and auxiliary Green's
functions involving the background source and the gluonic anti-field; these
latter Green's functions are subsequently related by means of a Schwinger-Dyson
type of equation to the ghost Green's functions appearing in the aforementioned
Slavnov-Taylor identity.Comment: 45 pages, uses axodraw; typos corrected, one figure changed, final
version to appear in Phys.Rev.
Confinement and Chiral Symmetry Breaking via Domain-Like Structures in the QCD Vacuum
A qualitative mechanism for the emergence of domain structured background
gluon fields due to singularities in gauge field configurations is considered,
and a model displaying a type of mean field approximation to the QCD partition
function based on this mechanism is formulated. Estimation of the vacuum
parameters (gluon condensate, topological susceptibility, string constant and
quark condensate) indicates that domain-like structures lead to an area law for
the Wilson loop, nonzero topological susceptibility and spontaneous breakdown
of chiral symmetry. Gluon and ghost propagators in the presence of domains are
calculated explicitly and their analytical properties are discussed. The
Fourier transforms of the propagators are entire functions and thus describe
confined dynamical fields.Comment: RevTeX, 48 pages (32 pages + Appendices A-E), new references added
[1,2,4,5] and minor formulae corrected for typographical error
On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes
The sensitivity of a search for sources of TeV neutrinos can be improved by
grouping potential sources together into generic classes in a procedure that is
known as source stacking. In this paper, we define catalogs of Active Galactic
Nuclei (AGN) and use them to perform a source stacking analysis. The grouping
of AGN into classes is done in two steps: first, AGN classes are defined, then,
sources to be stacked are selected assuming that a potential neutrino flux is
linearly correlated with the photon luminosity in a certain energy band (radio,
IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino
production in AGN, this correlation is motivated by hadronic AGN models, as
briefly reviewed in this paper.
The source stacking search for neutrinos from generic AGN classes is
illustrated using the data collected by the AMANDA-II high energy neutrino
detector during the year 2000. No significant excess for any of the suggested
groups was found.Comment: 43 pages, 12 figures, accepted by Astroparticle Physic
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