1,430 research outputs found
The ethics of CYP2D6 testing for patients considering tamoxifen
The CYP2D6 gene is responsible for the majority of tamoxifen metabolism. Recent compelling, yet limited data have determined that postmenopausal women who carry a functional polymorphism in the CYP2D6 gene have a worse clinical outcome than women who have a wild-type genotype. In this commentary we discuss the level of evidence needed to change clinical practice and whether CYP2D6 genotyping is appropriate for all women considering tamoxifen as part of their adjuvant therapy
Prediction of lethal and synthetically lethal knock-outs in regulatory networks
The complex interactions involved in regulation of a cell's function are
captured by its interaction graph. More often than not, detailed knowledge
about enhancing or suppressive regulatory influences and cooperative effects is
lacking and merely the presence or absence of directed interactions is known.
Here we investigate to which extent such reduced information allows to forecast
the effect of a knock-out or a combination of knock-outs. Specifically we ask
in how far the lethality of eliminating nodes may be predicted by their network
centrality, such as degree and betweenness, without knowing the function of the
system. The function is taken as the ability to reproduce a fixed point under a
discrete Boolean dynamics. We investigate two types of stochastically generated
networks: fully random networks and structures grown with a mechanism of node
duplication and subsequent divergence of interactions. On all networks we find
that the out-degree is a good predictor of the lethality of a single node
knock-out. For knock-outs of node pairs, the fraction of successors shared
between the two knocked-out nodes (out-overlap) is a good predictor of
synthetic lethality. Out-degree and out-overlap are locally defined and
computationally simple centrality measures that provide a predictive power
close to the optimal predictor.Comment: published version, 10 pages, 6 figures, 2 tables; supplement at
http://www.bioinf.uni-leipzig.de/publications/supplements/11-01
Kerr-CFT From Black-Hole Thermodynamics
We analyze the near-horizon limit of a general black hole with two commuting
killing vector fields in the limit of zero temperature. We use black hole
thermodynamics methods to relate asymptotic charges of the complete spacetime
to those obtained in the near-horizon limit. We then show that some
diffeomorphisms do alter asymptotic charges of the full spacetime, even though
they are defined in the near horizon limit and, therefore, count black hole
states. We show that these conditions are essentially the same as considered in
the Kerr/CFT corresponcence. From the algebra constructed from these
diffeomorphisms, one can extract its central charge and then obtain the black
hole entropy by use of Cardy's formula.Comment: 19 pages, JHEP3, no figures. V2: References added, small typos fixe
On Holographic description of the Kerr-Newman-AdS-dS black holes
In this paper, we study the holographic description of the generic
four-dimensional non-extremal Kerr-Newman-AdS-dS black holes. We find that if
focusing on the near-horizon region, for the massless scalar scattering in the
low-frequency limit, there exists hidden conformal symmetry on the solution
space. Similar to the Kerr case, this suggests that the Kerr-Newman-AdS-dS
black hole is dual to a two-dimensional CFT with central charges
and temperatures
. The macroscopic Bekenstein-Hawking
entropy could be recovered from the microscopic counting in dual CFT via the
Cardy formula. Using the Minkowski prescription, we compute the real-time
correlators of the scalar, photon and graviton in near horizon geometry of near
extremal Kerr-AdS-dS black hole. In all these cases, the retarded Green's
function and the corresponding absorption cross section are in perfect match
with CFT prediction. We further discuss the low-frequency scattering of a
charged scalar by a Kerr-Newman-AdS-dS black hole and find the dual CFT
description.Comment: 22 pages; minor corrections, conlusion unchanged, references
added;published versio
The environmental security debate and its significance for climate change
Policymakers, military strategists and academics all increasingly hail climate change as a security issue. This article revisits the (comparatively) long-standing âenvironmental security debateâ and asks what lessons that earlier debate holds for the push towards making climate change a security issue. Two important claims are made. First, the emerging climate security debate is in many ways a re-run of the earlier dispute. It features many of the same proponents and many of the same disagreements. These disagreements concern, amongst other things, the nature of the threat, the referent object of security and the appropriate policy responses. Second, given its many different interpretations, from an environmentalist perspective, securitisation of the climate is not necessarily a positive development
Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars
A knowledge of stellar ages is crucial for our understanding of many
astrophysical phenomena, and yet ages can be difficult to determine. As they
become older, stars lose mass and angular momentum, resulting in an observed
slowdown in surface rotation. The technique of 'gyrochronology' uses the
rotation period of a star to calculate its age. However, stars of known age
must be used for calibration, and, until recently, the approach was untested
for old stars (older than 1 gigayear, Gyr). Rotation periods are now known for
stars in an open cluster of intermediate age (NGC 6819; 2.5 Gyr old), and for
old field stars whose ages have been determined with asteroseismology. The data
for the cluster agree with previous period-age relations, but these relations
fail to describe the asteroseismic sample. Here we report stellar evolutionary
modelling, and confirm the presence of unexpectedly rapid rotation in stars
that are more evolved than the Sun. We demonstrate that models that incorporate
dramatically weakened magnetic braking for old stars can---unlike existing
models---reproduce both the asteroseismic and the cluster data. Our findings
might suggest a fundamental change in the nature of ageing stellar dynamos,
with the Sun being close to the critical transition to much weaker magnetized
winds. This weakened braking limits the diagnostic power of gyrochronology for
those stars that are more than halfway through their main-sequence lifetimes.Comment: 25 pages, 3 figures in main paper, 6 extended data figures, 1 table.
Published in Nature, January 2016. Please see https://youtu.be/O6HzYgP5uyc
for a video description of the resul
Cardy and Kerr
The Kerr/CFT correspondence employs the Cardy formula to compute the entropy
of the left moving CFT states. This computation, which correctly reproduces the
Bekenstein--Hawking entropy of the four-dimensional extremal Kerr black hole,
is performed in a regime where the temperature is of order unity rather than in
a high-temperature regime. We show that the comparison of the entropy of the
extreme Kerr black hole and the entropy in the CFT can be understood within the
Cardy regime by considering a D0-D6 system with the same entropic properties.Comment: 20 pages; LaTeX; JHEP format; v.2 references added, v.3 Section 4
adde
High Energy Neutrinos from Quasars
We review and clarify the assumptions of our basic model for neutrino
production in the cores of quasars, as well as those modifications to the model
subsequently made by other workers. We also present a revised estimate of the
neutrino background flux and spectrum obtained using more recent empirical
studies of quasars and their evolution. We compare our results with other
thoeretical calculations and experimental upper limits on the AGN neutrino
background flux. We also estimate possible neutrino fluxes from the jets of
blazars detected recently by the EGRET experiment on the Compton Gamma Ray
Observatory. We discuss the theoretical implications of these estimates.Comment: 14 pg., ps file (includes figures), To be published in Space Science
Review
Kerr/CFT, dipole theories and nonrelativistic CFTs
We study solutions of type IIB supergravity which are SL(2,R) x SU(2) x
U(1)^2 invariant deformations of AdS_3 x S^3 x K3 and take the form of products
of self-dual spacelike warped AdS_3 and a deformed three-sphere. One of these
backgrounds has been recently argued to be relevant for a derivation of
Kerr/CFT from string theory, whereas the remaining ones are holographic duals
of two-dimensional dipole theories and their S-duals. We show that each of
these backgrounds is holographically dual to a deformation of the DLCQ of the
D1-D5 CFT by a specific supersymmetric (1,2) operator, which we write down
explicitly in terms of twist operators at the free orbifold point. The
deforming operator is argued to be exactly marginal with respect to the
zero-dimensional nonrelativistic conformal (or Schroedinger) group - which is
simply SL(2,R)_L x U(1)_R. Moreover, in the supergravity limit of large N and
strong coupling, no other single-trace operators are turned on. We thus propose
that the field theory duals to the backgrounds of interest are nonrelativistic
CFTs defined by adding the single Schroedinger-invariant (1,2) operator
mentioned above to the original CFT action. Our analysis indicates that the
rotating extremal black holes we study are best thought of as finite
right-moving temperature (non-supersymmetric) states in the above-defined
supersymmetric nonrelativistic CFT and hints towards a more general connection
between Kerr/CFT and two-dimensional non-relativistic CFTs.Comment: 48+8 pages, 4 figures; minor corrections and references adde
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