3,586 research outputs found
New physical characterization of the Fontana Lapilli basaltic Plinian eruption, Nicaragua
The Fontana Lapilli deposit was erupted in the late Pleistocene from a vent, or multiple vents, located near Masaya volcano (Nicaragua) and is the product of one of the largest basaltic Plinian eruptions studied so far. This eruption evolved from an initial sequence of fluctuating fountain-like events and moderately explosive pulses to a sustained Plinian episode depositing fall beds of highly vesicular basaltic-andesite scoria (SiO2 >â53wt%). Samples show unimodal grain size distribution and a moderate sorting that are uniform in time. The juvenile component predominates (>â96wt%) and consists of vesicular clasts with both sub-angular and fluidal, elongated shapes. We obtain a maximum plume height of 32km and an associated mass eruption rate of 1.4 Ă 108kg sâ1 for the Plinian phase. Estimates of erupted volume are strongly sensitive to the technique used for the calculation and to the distribution of field data. Our best estimate for the erupted volume of the majority of the climactic Plinian phase is between 2.9 and 3.8km3 and was obtained by applying a power-law fitting technique with different integration limits. The estimated eruption duration varies between 4 and 6h. Marine-core data confirm that the tephra thinning is better fitted by a power-law than by an exponential tren
Hopf instantons and the Liouville equation in target space
We generalise recent results on Hopf instantons in a Chern--Simons and
Fermion theory in a fixed background magnetic field. We find that these
instanton solutions have to obey the Liouville equation in target space. As a
consequence, these solutions are given by a class of Hopf maps that consist of
the composition of the standard Hopf map with an arbitrary rational map.Comment: Latex file, 11 pages, no figure
Percutaneous angioplasty for infrainguinal graft-related stenoses
Objective:To assess the success of percutaneous transluminal angioplasty (PTA) in treating infrainguinal graft-related stenoses.Design:Retrospective analysis of stenoses undergoing PTA over 6 years.Materials:Fifty-seven stenoses in 42 grafts.Methods:Site, length and type of stenoses recorded. Follow-up till discharge, graft occlusion or death.Results:PTA was successful in 48/57 stenoses in 36 grafts (G), with a poor result in seven. Further PTA was required in seven stenoses (7 G). One graft occluded at PTA and one stenosis was inaccessible. Overall graft (G) patency (median 13 months) was 82% (1 year patency 84%). Of 48 successful PTAs (37 G), 36 remained patent (28 G), eight (4 G) occluded and four were lost to follow-up (4 G). Fourteen of thirty-six stenoses which remained patent required further intervention (seven PTA, six jump grafts, one vein patch). The four occlusions were associated with small veins (two), multiple stenoses (one) and a PTFE graft which occluded 10 days following PTA. Of the seven PTAs with a poor angiographic result, five remained patent, three after further intervention.Conclusion:PTA is the best treatment for localised stenoses. Stenoses >2 cm or multiple (three or more) stenoses are best treated surgically. Follow-up is essential, as 20% require further intervention
Static Axially Symmetric Einstein-Yang-Mills-Dilaton Solutions: II.Black Hole Solutions
We discuss the new class of static axially symmetric black hole solutions
obtained recently in Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton
theory. These black hole solutions are asymptotically flat and they possess a
regular event horizon. The event horizon is almost spherically symmetric with a
slight elongation along the symmetry axis. The energy density of the matter
fields is angle-dependent at the horizon. The static axially symmetric black
hole solutions satisfy a simple relation between mass, dilaton charge, entropy
and temperature. The black hole solutions are characterized by two integers,
the winding number and the node number of the purely magnetic gauge
field. With increasing node number the magnetically neutral black hole
solutions form sequences tending to limiting solutions with magnetic charge
, corresponding to Einstein-Maxwell-dilaton black hole solutions for finite
dilaton coupling constant and to Reissner-Nordstr\o m black hole solutions for
vanishing dilaton coupling constant.Comment: 41 pages including 45 postscript figures, RevTex forma
The bubbles of matter from multiskyrmions
The multiskyrmions with large baryon number B given by rational map (RM)
ansaetze can be described reasonably well within the domain wall approximation,
or as spherical bubbles with energy and baryon number density concentrated at
their boundary. A special class of profile functions is considered
approximating the true profile and domain wall behaviour at the same time. An
upper bound is obtained for the masses of RM multiskyrmions which is close to
the calculated masses, especially at large B. The gap between rigorous upper
and lower bounds for large B multiskyrmions is less than 4%. The basic
properties of such bubbles of matter are investigated, some of them being of
universal character, i.e. they do not depend on baryon number of configuration
and on the number of flavors. As a result, the lagrangian of the Skyrme type
models provides field theoretical realization of the bag model of special kind.Comment: 7 pages, no figure
Axially Symmetric Monopoles and Black Holes in Einstein-Yang-Mills-Higgs Theory
We investigate static axially symmetric monopole and black hole solutions
with magnetic charge n > 1 in Einstein-Yang-Mills-Higgs theory. For vanishing
and small Higgs selfcoupling, multimonopole solutions are gravitationally
bound. Their mass per unit charge is lower than the mass of the n=1 monopole.
For large Higgs selfcoupling only a repulsive phase exists. The static axially
symmetric hairy black hole solutions possess a deformed horizon with constant
surface gravity. We consider their properties in the isolated horizon
framework, interpreting them as bound states of monopoles and black holes.
Representing counterexamples to the ``no-hair'' conjecture, these black holes
are neither uniquely characterized by their horizon area and horizon charge.Comment: 23 Revtex pages, 43 Postscript figure
Hypernuclei as chiral solitons
The identification of flavored multiskyrmions with the ground states of known
hypernuclei is successful for several of them, e.g. for isodoublet H(Lambda) -
He(Lambda), A=4, isoscalars He(Lambda) (A=5) and Li(Lambda) (A=7). In other
cases agreement is not so good, but the behaviour of the binding energy with
increasing baryon number is in qualitative agreement with data. Charmed or
beauty hypernuclei within this approach are predicted to be bound stronger than
strange hypernuclei. This conclusion is stable against variation of poorly
known heavy flavor decay constants.Comment: 9 pages, 1 Fig. Presented at the International Workshops on Nuclear
and Particle Physics at 50-Gev PS, NP01 (KEK, Japan, December 2001) and NP02
(Kyoto, Japan, September 2002). Some additions and corrections of numerical
results are mad
Non-Relativistic Fermions Coupled to Transverse Gauge-Fields: The Single-Particle Green's Function in Arbitrary Dimension
We use a bosonization approach to calculate the single-particle Green's
function of non-relativistic fermions coupled to
transverse gauge-fields in arbitrary dimension . We find that in
transverse gauge-fields do not destroy the Fermi liquid, although for
the quasi-particle damping is anomalously large. For the
quasi-particle residue vanishes as
, where
is the Thomas-Fermi wave-vector, is the mass of the electrons, and
is the velocity of the gauge-particle. In the system is a Luttinger
liquid, with anomalous dimension
. For we
find that decays exponentially at large distances.Comment: RevTex, no figures
Correlation functions of higher-dimensional Luttinger liquids
Using higher-dimensional bosonization, we study correlation functions of
fermions with singular forward scattering. Following Bares and Wen [Phys. Rev.
B 48, 8636 (1993)], we consider density-density interactions in d dimensions
that diverge for small momentum transfers as q^{- eta} with eta = 2 (d-1). In
this case the single-particle Green's function shows Luttinger liquid behavior.
We discuss the momentum distribution and the density of states and show that,
in contrast to d=1, in higher dimensions the scaling behavior cannot be
characterized by a single anomalous exponent. We also calculate the irreducible
polarization for q close to 2 k_F and show that the leading singularities
cancel. We discuss consequences for the effect of disorder on
higher-dimensional Luttinger liquids.Comment: 7 RevTex pages, 2 figures, minor modifications, to appear in Phys.
Rev. B (Feb. 1999
Transfer of gene corrected T cells corrects humoral and cytotoxic defects in X-linked lymphoproliferative disease (XLP1)
BACKGROUND: XLP1 arises from mutations in the SH2D1A gene encoding SAP, an adaptor protein expressed in T, NK and NKT cells. Defects lead to abnormalities of T and NK cell cytotoxicity and T cell dependent humoral function. Clinical manifestations include haemophagocytic lymphohistiocytosis (HLH), lymphoma and dysgammaglobulinaemia. Curative treatment is limited to haematopoietic stem cell transplant with outcome reliant on a good donor match. OBJECTIVES: As most symptoms arise from defective T cell function, we investigated whether transfer of SAP gene corrected T cells could reconstitute known effector cell defects. METHODS: CD3+ lymphocytes from sap-deficient mice were transduced with a gammaretroviral vector encoding human SAP cDNA before transfer into sub-lethally irradiated sap-deficient recipients. Following immunisation with the T-dependent antigen NP-CGG, recovery of humoral function was evaluated through germinal centre formation and antigen specific responses. To efficiently transduce patient CD3+ cells, we generated an equivalent lentiviral SAP vector. Functional recovery was demonstrated using in vitro cytotoxicity and TFH cell function assays, alongside tumour clearance in an in vivo LCL lymphoma xenograft model. RESULTS: In sap-deficient mice, 20-40% engraftment of gene modified T cells led to significant recovery of germinal centre formation and NP-specific antibody responses. Gene corrected patient T cells demonstrated improved cytotoxicity and TFH cell function in vitro. Adoptive transfer of gene corrected patient CTLs reduced tumour burden to a level comparable with healthy donor CTLs in an in vivo lymphoma model. CONCLUSIONS: These data demonstrate that autologous T cell gene therapy corrects SAP dependent defects and may offer an alternative therapeutic option for XLP1 patients
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