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Oncogenic Gain of Function in Glioblastoma Is Linked to Mutant p53 Amyloid Oligomers.
Tumor-associated p53 mutations endow cells with malignant phenotypes, including chemoresistance. Amyloid-like oligomers of mutant p53 transform this tumor suppressor into an oncogene. However, the composition and distribution of mutant p53 oligomers are unknown and the mechanism involved in the conversion is sparse. Here, we report accumulation of a p53 mutant within amyloid-like p53 oligomers in glioblastoma-derived cells presenting a chemoresistant gain-of-function phenotype. Statistical analysis from fluorescence fluctuation spectroscopy, pressure-induced measurements, and thioflavin T kinetics demonstrates the distribution of oligomers larger than the active tetrameric form of p53 in the nuclei of living cells and the destabilization of native-drifted p53 species that become amyloid. Collectively, these results provide insights into the role of amyloid-like mutant p53 oligomers in the chemoresistance phenotype of malignant and invasive brain tumors and shed light on therapeutic options to avert cancer
The Wasteland of Random Supergravities
We show that in a general \cal{N} = 1 supergravity with N \gg 1 scalar
fields, an exponentially small fraction of the de Sitter critical points are
metastable vacua. Taking the superpotential and Kahler potential to be random
functions, we construct a random matrix model for the Hessian matrix, which is
well-approximated by the sum of a Wigner matrix and two Wishart matrices. We
compute the eigenvalue spectrum analytically from the free convolution of the
constituent spectra and find that in typical configurations, a significant
fraction of the eigenvalues are negative. Building on the Tracy-Widom law
governing fluctuations of extreme eigenvalues, we determine the probability P
of a large fluctuation in which all the eigenvalues become positive. Strong
eigenvalue repulsion makes this extremely unlikely: we find P \propto exp(-c
N^p), with c, p being constants. For generic critical points we find p \approx
1.5, while for approximately-supersymmetric critical points, p \approx 1.3. Our
results have significant implications for the counting of de Sitter vacua in
string theory, but the number of vacua remains vast.Comment: 39 pages, 9 figures; v2: fixed typos, added refs and clarification
The Conformal Anomaly of M5-Branes
We show that the conformal anomaly for N M5-branes grows like . The
method we employ relates Coulomb branch interactions in six dimensions to
interactions in four dimensions using supersymmetry. This leads to a relation
between the six-dimensional conformal anomaly and the conformal anomaly of N=4
Yang-Mills. Along the way, we determine the structure of the four derivative
interactions for the toroidally compactified (2,0) theory, while encountering
interesting novelties in the structure of the six derivative interactions.Comment: 38 pages, LaTeX; references adde
Six-dimensional (1,0) effective action of F-theory via M-theory on Calabi-Yau threefolds
The six-dimensional effective action of F-theory compactified on a singular
elliptically fibred Calabi-Yau threefold is determined by using an M-theory
lift. The low-energy data are derived by comparing a circle reduction of a
general six-dimensional (1,0) gauged supergravity theory with the effective
action of M-theory on the resolved Calabi-Yau threefold. The derivation
includes six-dimensional tensor multiplets for which the (anti-) self-duality
constraints are imposed on the level of the five-dimensional action. The vector
sector of the reduced theory is encoded by a non-standard potential due to the
Green-Schwarz term in six dimensions. This Green-Schwarz term also contains
higher curvature couplings which are considered to establish the full map
between anomaly coefficients and geometry. F-/M-theory duality is exploited by
moving to the five-dimensional Coulomb branch after circle reduction and
integrating out massive vector multiplets and matter hypermultiplets. The
associated fermions then generate additional Chern-Simons couplings at
one-loop. Further couplings involving the graviphoton are induced by quantum
corrections due to excited Kaluza-Klein modes. On the M-theory side integrating
out massive fields corresponds to resolving the singularities of the Calabi-Yau
threefold, and yields intriguing relations between six-dimensional anomalies
and classical topology.Comment: 55 pages, v2: typos corrected, discussion of loop corrections
improve
An inhibitory pull-push circuit in frontal cortex.
Push-pull is a canonical computation of excitatory cortical circuits. By contrast, we identify a pull-push inhibitory circuit in frontal cortex that originates in vasoactive intestinal polypeptide (VIP)-expressing interneurons. During arousal, VIP cells rapidly and directly inhibit pyramidal neurons; VIP cells also indirectly excite these pyramidal neurons via parallel disinhibition. Thus, arousal exerts a feedback pull-push influence on excitatory neurons-an inversion of the canonical push-pull of feedforward input
Seiberg duality for Chern-Simons quivers and D-brane mutations
Chern-Simons quivers for M2-branes at Calabi-Yau singularities are best
understood as the low energy theory of D2-branes on a dual type IIA background.
We show how the D2-brane point of view naturally leads to three dimensional
Seiberg dualities for Chern-Simons quivers with chiral matter content: They
arise from a change of brane basis (or mutation), in complete analogy with the
better known Seiberg dualities for D3-brane quivers. This perspective
reproduces the known rules for Seiberg dualities in Chern-Simons-Yang-Mills
theories with unitary gauge groups. We provide explicit examples of dual
theories for the quiver dual to the Y^{p,q}(CP^2) geometries. We also comment
on the string theory derivation of CS quivers dual to massive type IIA
geometries.Comment: 32 pages+appendix; v2: added a referenc
Decompactifications and Massless D-Branes in Hybrid Models
A method of determining the mass spectrum of BPS D-branes in any phase limit
of a gauged linear sigma model is introduced. A ring associated to monodromy is
defined and one considers K-theory to be a module over this ring. A simple but
interesting class of hybrid models with Landau-Ginzburg fibres over CPn are
analyzed using special Kaehler geometry and D-brane probes. In some cases the
hybrid limit is an infinite distance in moduli space and corresponds to a
decompactification. In other cases the hybrid limit is at a finite distance and
acquires massless D-branes. An example studied appears to correspond to a novel
theory of supergravity with an SU(2) gauge symmetry where the gauge and
gravitational couplings are necessarily tied to each other.Comment: PDF-LaTeX, 34 pages, 2 mps figure
Non-abelian Action for Multiple Five-Branes with Self-Dual Tensors
We construct an action for non-abelian 2-form in 6-dimensions. Our action
consists of a non-abelian generalization of the abelian action of Perry and
Schwarz for a single five-brane. It admits a self-duality equation on the field
strength as the equation of motion. It has a modified 6d Lorentz symmetry. On
dimensional reduction on a circle, our action gives the standard 5d Yang-Mills
action plus higher order corrections. Based on these properties, we propose
that our theory describes the gauge sector of multiple M5-branes in flat space.Comment: LaTeX, 26 pages. v2: improved discussion of Lorentz symmetry. ref
added. v3: add comments in the discussion section on the inclusion of scalar
fields and supersymmetry; title changed to a more suitable one; version
published in JHE
On instantons as Kaluza-Klein modes of M5-branes
Instantons and W-bosons in 5d maximally supersymmetric Yang-Mills theory
arise from a circle compactification of the 6d (2,0) theory as Kaluza-Klein
modes and winding self-dual strings, respectively. We study an index which
counts BPS instantons with electric charges in Coulomb and symmetric phases. We
first prove the existence of unique threshold bound state of (noncommutative)
U(1) instantons for any instanton number, and also show that charged instantons
in the Coulomb phase correctly give the degeneracy of SU(2) self-dual strings.
By studying SU(N) self-dual strings in the Coulomb phase, we find novel
momentum-carrying degrees on the worldsheet. The total number of these degrees
equals the anomaly coefficient of SU(N) (2,0) theory. We finally show that our
index can be used to study the symmetric phase of this theory, and provide an
interpretation as the superconformal index of the sigma model on instanton
moduli space.Comment: 54 pages, 2 figures. v2: references added, figure improved, added
comments on self-dual string anomaly, added new materials on the symmetric
phase index, other minor correction
Development of a decision support tool to facilitate primary care management of patients with abnormal liver function tests without clinically apparent liver disease [HTA03/38/02]. Abnormal Liver Function Investigations Evaluation (ALFIE)
Liver function tests (LFTs) are routinely performed in primary care, and are often the gateway to further invasive and/or expensive investigations. Little is known of the consequences in people with an initial abnormal liver function (ALF) test in primary care and with no obvious liver disease. Further investigations may be dangerous for the patient and expensive for Health Services. The aims of this study are to determine the natural history of abnormalities in LFTs before overt liver disease presents in the population and identify those who require minimal further investigations with the potential for reduction in NHS costs
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