1,780 research outputs found
Holographic phase diagram of quark-gluon plasma formed in heavy-ions collisions
The phase diagram of quark gluon plasma (QGP) formed at a very early stage
just after the heavy ion collision is obtained by using a holographic dual
model for the heavy ion collision. In this dual model colliding ions are
described by the charged shock gravitational waves. Points on the phase diagram
correspond to the QGP or hadronic matter with given temperatures and chemical
potentials. The phase of QGP in dual terms is related to the case when the
collision of shock waves leads to formation of trapped surface. Hadronic matter
and other confined states correspond to the absence of trapped surface after
collision.
Multiplicity of the ion collision process is estimated in the dual language
as area of the trapped surface. We show that a non-zero chemical potential
reduces the multiplicity. To plot the phase diagram we use two different dual
models of colliding ions, the point and the wall shock waves, and find
qualitative agreement of the results.Comment: 33 pages, 14 figures, typos correcte
In-situ upgrading of Napier grass pyrolysis vapour over microporous and hierarchical mesoporous zeolites
This study presents in-situ upgrading of pyrolysis
vapour derived from Napier grass over microporous and
mesoporous ZSM-5 catalysts. It evaluates effect of process
variables such catalystâbiomass ratio and catalyst type in
a vertical fixed bed pyrolysis system at 600 °C, 50 °C/min
under 5 L/min nitrogen flow. Increasing catalystâbiomass
ratio during the catalytic process with microporous structure
reduced production of organic phase bio-oil by approximately
7.0 wt%. Using mesoporous catalyst promoted
nearly 4.0 wt% higher organic yield relative to microporous
catalyst, which translate to only about 3.0 wt% reduction
in organic phase compared to the yield of organic phase
from non-catalytic process. GCâMS analysis of bio-oil
organic phase revealed maximum degree of deoxygenation
of about 36.9% with microporous catalyst compared to
the mesoporous catalysts, which had between 39 and 43%.
Mesoporous catalysts promoted production olefins and
alkanes, normal phenol, monoaromatic hydrocarbons while
microporous catalyst favoured the production of alkenes
and polyaromatic hydrocarbons. There was no significant increase in the production of normal phenols over microporous catalyst due to its inability to transform the methoxyphenols and methoxy aromatics. This study demonstrated that upgrading of Napier grass pyrolysis vapour over mesoporous ZSM-5 produced bio-oil with improved physicochemical properties
Critical Trapped Surfaces Formation in the Collision of Ultrarelativistic Charges in (A)dS
We study the formation of marginally trapped surfaces in the head-on
collision of two ultrarelativistic charges in space-time. The metric of
ultrarelativistic charged particles in is obtained by boosting
Reissner-Nordstr\"om space-time to the speed of light. We show that
formation of trapped surfaces on the past light cone is only possible when
charge is below certain critical - situation similar to the collision of two
ultrarelativistic charges in Minkowski space-time. This critical value depends
on the energy of colliding particles and the value of a cosmological constant.
There is richer structure of critical domains in case. In this case
already for chargeless particles there is a critical value of the cosmological
constant only below which trapped surfaces formation is possible. Appearance of
arbitrary small nonzero charge significantly changes the physical picture.
Critical effect which has been observed in the neutral case does not take place
more. If the value of the charge is not very large solution to the equation on
trapped surface exists for any values of cosmological radius and energy density
of shock waves. Increasing of the charge leads to decrease of the trapped
surface area, and at some critical point the formation of trapped surfaces of
the type mentioned above becomes impossible.Comment: 30 pages, Latex, 7 figures, Refs. added and typos correcte
On effective actions of BPS branes and their higher derivative corrections
We calculate in detail the disk level S-matrix element of one Ramond-Ramond
field and three gauge field vertex operators in the world volume of BPS branes,
to find four gauge field couplings to all orders of up to on-shell
ambiguity. Then using these infinite couplings we find that the massless pole
of the field theory amplitude is exactly equal to the massless pole S-matrix
element of this amplitude for the case to all orders of .
Finally we show that the infinite massless poles and the contact terms of this
amplitude for the case can be reproduced by the Born-Infeld action and
the Wess-Zumino actions and by their higher derivative corrections.Comment: 26 pages, 2 figures, minor corrections,references added and version
published in JHE
Perivascular epithelioid cell tumor of the retroperitoneum in a young woman resulting in an abdominal chyloma
Perivascular epithelioid cell tumor (PEComa) is an extremely rare neoplasm which appears to have predominancy for young, frequently Asian, women. The neoplasm is composed chiefly of HMB-45-positive epithelioid cells with clear to granular cytoplasm and usually showing a perivascular distribution. These tumors have been reported in various organs under a variety of designations. Malignant PEComas exist but are very rare. The difficulty in determining optimal therapy, owing to the sparse literature available, led us to present this case. We report a retroperitoneal PEComa discovered during emergency surgery for abdominal pain in a 28-year-old Asian woman. The postoperative period was complicated by chylous ascites that was initially controlled by a wait-and-see policy with total parenteral nutrition. However, the chyle production gradually increased to more than 4 l per day. The development of a bacterial peritonitis resulted in cessation of production of abdominal fluid permitting normal nutrition without chylous leakage. Effective treatment for this rare complication of PEComa is not yet known; therefore, we have chosen to engage in long-term clinical follow-up
The non-Abelian gauge theory of matrix big bangs
We study at the classical and quantum mechanical level the time-dependent
Yang-Mills theory that one obtains via the generalisation of discrete
light-cone quantisation to singular homogeneous plane waves. The non-Abelian
nature of this theory is known to be important for physics near the
singularity, at least as far as the number of degrees of freedom is concerned.
We will show that the quartic interaction is always subleading as one
approaches the singularity and that close enough to t=0 the evolution is driven
by the diverging tachyonic mass term. The evolution towards asymptotically flat
space-time also reveals some surprising features.Comment: 29 pages, 8 eps figures, v2: minor changes, references added: v3
small typographical changes
The generalized cusp in ABJ(M) N = 6 Super Chern-Simons theories
We construct a generalized cusped Wilson loop operator in N = 6 super
Chern-Simons-matter theories which is locally invariant under half of the
supercharges. It depends on two parameters and interpolates smoothly between
the 1/2 BPS line or circle and a pair of antiparallel lines, representing a
natural generalization of the quark-antiquark potential in ABJ(M) theories. For
particular choices of the parameters we obtain 1/6 BPS configurations that,
mapped on S^2 by a conformal transformation, realize a three-dimensional
analogue of the wedge DGRT Wilson loop of N = 4. The cusp couples, in addition
to the gauge and scalar fields of the theory, also to the fermions in the
bifundamental representation of the U(N)xU(M) gauge group and its expectation
value is expressed as the holonomy of a suitable superconnection. We discuss
the definition of these observables in terms of traces and the role of the
boundary conditions of fermions along the loop. We perform a complete two-loop
analysis, obtaining an explicit result for the generalized cusp at the second
non-trivial order, from which we read off the interaction potential between
heavy 1/2 BPS particles in the ABJ(M) model. Our results open the possibility
to explore in the three-dimensional case the connection between localization
properties and integrability, recently advocated in D = 4.Comment: 53 pages, 10 figures, added references, this is the version appeared
on JHE
Electrified plasma in AdS/CFT correspondence
We construct new gravity backgrounds holographic dual to neutral plasma with
U(1) global symmetry in the presence of constant electric field, considering
its full back-reactions to the metric. As the electric field and the induced
current cause a net energy in-flow to the system, the plasma is continually
heated up and the corresponding gravity solution has an expanding horizon.
After proposing a consistent late-time expansion scheme, we present analytic
solutions in the scheme up to next-leading order, and our solutions are new
time-dependent solutions of 5D asymptotic AdS Einstein-Maxwell(-Chern-Simons)
theory. To extract dual CFT stress tensor and U(1) current from the solutions,
we perform a rigorous holographic renormalization of
Einstein-Maxwell-Chern-Simons theory including full back-reactions, which can
in itself be an interesting addition to literatures. As by-products, we obtain
interesting modifications of energy-momentum/current Ward identities due to the
U(1) symmetry and its triangle anomaly.Comment: 27 pages, no figure, v3, minor typos fixed, matches with published
versio
The Combinatorics of Alternating Tangles: from theory to computerized enumeration
We study the enumeration of alternating links and tangles, considered up to
topological (flype) equivalences. A weight is given to each connected
component, and in particular the limit yields information about
(alternating) knots. Using a finite renormalization scheme for an associated
matrix model, we first reduce the task to that of enumerating planar
tetravalent diagrams with two types of vertices (self-intersections and
tangencies), where now the subtle issue of topological equivalences has been
eliminated. The number of such diagrams with vertices scales as for
. We next show how to efficiently enumerate these diagrams (in time
) by using a transfer matrix method. We give results for various
generating functions up to 22 crossings. We then comment on their large-order
asymptotic behavior.Comment: proceedings European Summer School St-Petersburg 200
Consensus criteria for sensitive detection of minimal neuroblastoma cells in bone marrow, blood and stem cell preparations by immunocytology and QRT-PCR: recommendations by the International Neuroblastoma Risk Group Task Force
Disseminating disease is a predictive and prognostic indicator of poor outcome in children with neuroblastoma. Its accurate and sensitive assessment can facilitate optimal treatment decisions. The International Neuroblastoma Risk Group (INRG) Task Force has defined standardised methods for the determination of minimal disease (MD) by immunocytology (IC) and quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) using disialoganglioside GD2 and tyrosine hydroxylase mRNA respectively. The INRG standard operating procedures (SOPs) define methods for collecting, processing and evaluating bone marrow (BM), peripheral blood (PB) and peripheral blood stem cell harvest by IC and QRT-PCR. Sampling PB and BM is recommended at diagnosis, before and after myeloablative therapy and at the end of treatment. Peripheral blood stem cell products should be analysed at the time of harvest. Performing MD detection according to INRG SOPs will enable laboratories throughout the world to compare their results and thus facilitate quality-controlled multi-centre prospective trials to assess the clinical significance of MD and minimal residual disease in heterogeneous patient groups
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