1,190 research outputs found
Sugawara-type constraints in hyperbolic coset models
In the conjectured correspondence between supergravity and geodesic models on
infinite-dimensional hyperbolic coset spaces, and E10/K(E10) in particular, the
constraints play a central role. We present a Sugawara-type construction in
terms of the E10 Noether charges that extends these constraints infinitely into
the hyperbolic algebra, in contrast to the truncated expressions obtained in
arXiv:0709.2691 that involved only finitely many generators. Our extended
constraints are associated to an infinite set of roots which are all imaginary,
and in fact fill the closed past light-cone of the Lorentzian root lattice. The
construction makes crucial use of the E10 Weyl group and of the fact that the
E10 model contains both D=11 supergravity and D=10 IIB supergravity. Our
extended constraints appear to unite in a remarkable manner the different
canonical constraints of these two theories. This construction may also shed
new light on the issue of `open constraint algebras' in traditional canonical
approaches to gravity.Comment: 49 page
Use of clofarabine for acute childhood leukemia
A second-generation of purine nucleoside analogs, starting with clofarabine, has been developed in the course of the search for new therapeutic agents for acute childhood leukemia, especially for refractory or relapsed disease. Clofarabine is a hybrid of fludarabine and cladribine, and has shown to have antileukemic activity in acute lymphoblastic leukemia as well as in myeloid disorders. As the only new antileukemic chemotherapeutic agent to enter clinical use in the last 10 years, clofarabine was approved as an orphan drug with the primary indication of use in pediatric patients. Toxicity has been tolerable in a heavily pretreated patient population, and clofarabine has been demonstrated to be safe, both as a single agent and in combination therapies. Liver dysfunction has been the most frequently observed adverse event, but this is generally reversible. Numerous Phase I and II trials have recently been conducted, and are still ongoing in an effort to find the optimal role for clofarabine in various treatment strategies. Concomitant use of clofarabine, cytarabine, and etoposide was confirmed to be safe and effective in two independent trials. Based on the promising results when used as a salvage regimen, clofarabine is now being investigated for its potential to become part of frontline protocols
Use of clofarabine for acute childhood leukemia.
A second-generation of purine nucleoside analogs, starting with clofarabine, has been developed in the course of the search for new therapeutic agents for acute childhood leukemia, especially for refractory or relapsed disease. Clofarabine is a hybrid of fludarabine and cladribine, and has shown to have antileukemic activity in acute lymphoblastic leukemia as well as in myeloid disorders. As the only new antileukemic chemotherapeutic agent to enter clinical use in the last 10 years, clofarabine was approved as an orphan drug with the primary indication of use in pediatric patients. Toxicity has been tolerable in a heavily pretreated patient population, and clofarabine has been demonstrated to be safe, both as a single agent and in combination therapies. Liver dysfunction has been the most frequently observed adverse event, but this is generally reversible. Numerous Phase I and II trials have recently been conducted, and are still ongoing in an effort to find the optimal role for clofarabine in various treatment strategies. Concomitant use of clofarabine, cytarabine, and etoposide was confirmed to be safe and effective in two independent trials. Based on the promising results when used as a salvage regimen, clofarabine is now being investigated for its potential to become part of frontline protocols
Colourful Poincaré symmetry, gravity and particle actions
We construct a generalisation of the three-dimensional Poincar\'e algebra that also includes a colour symmetry factor. This algebra can be used to define coloured Poincar\'e gravity in three space-time dimensions as well as to study generalisations of massive and massless free particle models. We present various such generalised particle models that differ in which orbits of the coloured Poincar\'e symmetry are described. Our approach can be seen as a stepping stone towards the description of particles interacting with a non-abelian background field or as a starting point for a worldline formulation of an associated quantum field theory
Functional mri of human brain activation combining high spatial and temporal resolution by a cine flash technique
Curvature corrections and Kac-Moody compatibility conditions
We study possible restrictions on the structure of curvature corrections to
gravitational theories in the context of their corresponding Kac--Moody
algebras, following the initial work on E10 in Class. Quant. Grav. 22 (2005)
2849. We first emphasize that the leading quantum corrections of M-theory can
be naturally interpreted in terms of (non-gravity) fundamental weights of E10.
We then heuristically explore the extent to which this remark can be
generalized to all over-extended algebras by determining which curvature
corrections are compatible with their weight structure, and by comparing these
curvature terms with known results on the quantum corrections for the
corresponding gravitational theories.Comment: 27 page
Eisenstein series for infinite-dimensional U-duality groups
We consider Eisenstein series appearing as coefficients of curvature
corrections in the low-energy expansion of type II string theory four-graviton
scattering amplitudes. We define these Eisenstein series over all groups in the
E_n series of string duality groups, and in particular for the
infinite-dimensional Kac-Moody groups E9, E10 and E11. We show that,
remarkably, the so-called constant term of Kac-Moody-Eisenstein series contains
only a finite number of terms for particular choices of a parameter appearing
in the definition of the series. This resonates with the idea that the constant
term of the Eisenstein series encodes perturbative string corrections in
BPS-protected sectors allowing only a finite number of corrections. We underpin
our findings with an extensive discussion of physical degeneration limits in
D<3 space-time dimensions.Comment: 69 pages. v2: Added references and small additions, to be published
in JHE
E10 and Gauged Maximal Supergravity
We compare the dynamics of maximal three-dimensional gauged supergravity in
appropriate truncations with the equations of motion that follow from a
one-dimensional E10/K(E10) coset model at the first few levels. The constant
embedding tensor, which describes gauge deformations and also constitutes an
M-theoretic degree of freedom beyond eleven-dimensional supergravity, arises
naturally as an integration constant of the geodesic model. In a detailed
analysis, we find complete agreement at the lowest levels. At higher levels
there appear mismatches, as in previous studies. We discuss the origin of these
mismatches.Comment: 34 pages. v2: added references and typos corrected. Published versio
Role of osmotic and hydrostatic pressures in bacteriophage genome ejection
A critical step in the bacteriophage life cycle is genome ejection into host
bacteria. The ejection process for double-stranded DNA phages has been studied
thoroughly \textit{in vitro}, where after triggering with the cellular receptor
the genome ejects into a buffer. The experimental data have been interpreted in
terms of the decrease in free energy of the densely packed DNA associated with
genome ejection. Here we detail a simple model of genome ejection in terms of
the hydrostatic and osmotic pressures inside the phage, a bacterium, and a
buffer solution/culture medium. We argue that the hydrodynamic flow associated
with the water movement from the buffer solution into the phage capsid and
further drainage into the bacterial cytoplasm, driven by the osmotic gradient
between the bacterial cytoplasm and culture medium, provides an alternative
mechanism for phage genome ejection \textit{in vivo}; the mechanism is
perfectly consistent with phage genome ejection \textit{in vitro}.Comment: 5 pages, 2 figures, references update
K(E9) from K(E10)
We analyse the M-theoretic generalisation of the tangent space structure
group after reduction of the D=11 supergravity theory to two space-time
dimensions in the context of hidden Kac-Moody symmetries. The action of the
resulting infinite-dimensional `R symmetry' group K(E9) on certain unfaithful,
finite-dimensional spinor representations inherited from K(E10) is studied. We
explain in detail how these representations are related to certain finite
codimension ideals within K(E9), which we exhibit explicitly, and how the
known, as well as new finite-dimensional `generalised holonomy groups' arise as
quotients of K(E9) by these ideals. In terms of the loop algebra realisations
of E9 and K(E9) on the fields of maximal supergravity in two space-time
dimensions, these quotients are shown to correspond to (generalised) evaluation
maps, in agreement with previous results of Nicolai and Samtleben
(hep-th/0407055). The outstanding question is now whether the related
unfaithful representations of K(E10) can be understood in a similar way.Comment: 35 pages; v2: References added; v3: Author, one reference and two
appendices added. Extended results in sections 3.2 and 4.
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