15,967 research outputs found
Further search for a neutral boson with a mass around 9 MeV/c2
Two dedicated experiments on internal pair conversion (IPC) of isoscalar M1
transitions were carried out in order to test a 9 MeV/c2 X-boson scenario. In
the 7Li(p,e+e-)8Be reaction at 1.1 MeV proton energy to the predominantly T=0
level at 18.15 MeV, a significant deviation from IPC was observed at large pair
correlation angles. In the 11B(d,n e+e-)12C reaction at 1.6 MeV, leading to the
12.71 MeV 1+ level with pure T=0 character, an anomaly was observed at 9
MeV/c2. The compatibility of the results with the scenario is discussed.Comment: 12 pages, 5 figures, 2 table
Acting without being in control: Exploring volition in Parkinson's disease with impulsive compulsive behaviours.
BACKGROUND: Several aspects of volitional control of action may be relevant in the pathophysiology of impulsive-compulsive behaviours (ICB) in Parkinson's disease (PD). We aimed to explore multiple aspects of action control, assessing reward-related behaviour, inhibition (externally and internally triggered) and sense of agency in PD patients, with and without ICB compared to healthy subjects. METHODS: Nineteen PD patients with ICB (PD-ICB), 19 PD without ICB (PD-no-ICB) and 19 healthy controls (HC) underwent a battery of tests including: Intentional Binding task which measures sense of agency; Stop Signal Reaction Time (SSRT) measuring capacity for reactive inhibition; the Marble task, assessing intentional inhibition; Balloon Analog Risk Task for reward sensitivity. RESULTS: One-way ANOVA showed significant main effect of group for action binding (p = 0.004, F = 6.27). Post hoc analysis revealed that PD-ICB had significantly stronger action binding than HC (p = 0.004), and PD-no-ICB (p = 0.04). There was no difference between PD-no-ICB and HC. SSRT did not differ between PD groups, whereas a significant difference between PD-no-ICB and HC was detected (p = 0.01). No other differences were found among groups in the other tasks. CONCLUSIONS: PD patients with ICB have abnormal performance on a psychophysical task assessing sense of agency, which might be related to a deficit in action representation at cognitive/experiential level. Yet, they have no deficit on tasks evaluating externally and internally triggered inhibitory control, or in reward-based decision-making. We conclude that impaired sense of agency may be a factor contributing to ICB in PD patients
In-flight measurements of energetic radiation from lightning and thunderclouds
In the certification procedure aircraft builders carry out so-called icing
tests flights, where the zero degree Celsius altitude is deliberately sought
and crossed in or under thunderstorms. Airbus also used these flights to test
ILDAS, a system aimed to determine lightning severity and attachment points
during flight from high speed data on the electric and magnetic field at the
aircraft surface. We used this unique opportunity to enhance the ILDAS systems
with two x-ray detectors coupled to high speed data recorders in an attempt to
determine the x-rays produced by lightning in-situ, with synchronous
determination of the lightning current distribution and electric field at the
aircraft. Such data are of interest in a study of lightning physics. In
addition, the data may provide clues to the x-ray dose for personnel and
equipment during flights. The icing campaign ran in April 2014; in six flights
we collected data of 61 lightning strikes on an Airbus test aircraft. In this
communication we briefly describe ILDAS and present selected results on three
strikes, two aircraft initiated and one intercepted. Most of the x-rays have
been observed synchronous with initiating negative leader steps, and as bursts
immediately preceding the current of the recoil process. Those processes
include the return stroke. The bursts last one to four micro-second and attain
x-ray energies up to 10 MeV. Intensity and spectral distribution of the x-rays
and the association with the current distribution are discussed. ILDAS also
continuously records x-rays at low resolution in time and amplitude.Comment: 28 pages, 9 figure
Black Hole Meiosis
The enumeration of BPS bound states in string theory needs refinement.
Studying partition functions of particles made from D-branes wrapped on
algebraic Calabi-Yau 3-folds, and classifying states using split attractor flow
trees, we extend the method for computing a refined BPS index, arXiv:0810.4301.
For certain D-particles, a finite number of microstates, namely polar states,
exclusively realized as bound states, determine an entire partition function
(elliptic genus). This underlines their crucial importance: one might call them
the `chromosomes' of a D-particle or a black hole. As polar states also can be
affected by our refinement, previous predictions on elliptic genera are
modified. This can be metaphorically interpreted as `crossing-over in the
meiosis of a D-particle'. Our results improve on hep-th/0702012, provide
non-trivial evidence for a strong split attractor flow tree conjecture, and
thus suggest that we indeed exhaust the BPS spectrum. In the D-brane
description of a bound state, the necessity for refinement results from the
fact that tachyonic strings split up constituent states into `generic' and
`special' states. These are enumerated separately by topological invariants,
which turn out to be partitions of Donaldson-Thomas invariants. As modular
predictions provide a check on many of our results, we have compelling evidence
that our computations are correct.Comment: 46 pages, 8 figures. v2: minor changes. v3: minor changes and
reference adde
Remarks on Finite W Algebras
The property of some finite W algebras to be the commutant of a particular
subalgebra of a simple Lie algebra G is used to construct realizations of G.
When G=so(4,2), unitary representations of the conformal and Poincare algebras
are recognized in this approach, which can be compared to the usual induced
representation technique. When G=sp(2,R) or sp(4,R), the anyonic parameter can
be seen as the eigenvalue of a W generator in such W representations of G. The
generalization of such properties to the affine case is also discussed in the
conclusion, where an alternative of the Wakimoto construction for sl(2) level k
is briefly presented. This mini review is based on invited talks presented by
P. Sorba at the ``Vth International Colloquium on Quantum Groups and Integrable
Systems'', Prague (Czech Republic), June 1996; ``Extended and Quantum Algebras
and their Applications to Physics'', Tianjin (China), August 1996; ``Selected
Topics of Theoretical and Modern Mathematical Physics'', Tbilisi (Georgia),
September 1996; to be published in the Proceedings.Comment: LaTeX, 16 pages, references adde
Time-resolved photometry of the young dipper RX~J1604.3-2130A:Unveiling the structure and mass transport through the innermost disk
Context. RX J1604.3-2130A is a young, dipper-type, variable star in the Upper Scorpius association, suspected to have an inclined inner disk, with respect to its face-on outer disk. Aims. We aim to study the eclipses to constrain the inner disk properties. Methods. We used time-resolved photometry from the Rapid Eye Mount telescope and Kepler 2 data to study the multi-wavelength variability, and archival optical and infrared data to track accretion, rotation, and changes in disk structure. Results. The observations reveal details of the structure and matter transport through the inner disk. The eclipses show 5 d quasi-periodicity, with the phase drifting in time and some periods showing increased/decreased eclipse depth and frequency. Dips are consistent with extinction by slightly processed dust grains in an inclined, irregularly-shaped inner disk locked to the star through two relatively stable accretion structures. The grains are located near the dust sublimation radius (similar to 0.06 au) at the corotation radius, and can explain the shadows observed in the outer disk. The total mass (gas and dust) required to produce the eclipses and shadows is a few % of a Ceres mass. Such an amount of mass is accreted/replenished by accretion in days to weeks, which explains the variability from period to period. Spitzer and WISE infrared variability reveal variations in the dust content in the innermost disk on a timescale of a few years, which is consistent with small imbalances (compared to the stellar accretion rate) in the matter transport from the outer to the inner disk. A decrease in the accretion rate is observed at the times of less eclipsing variability and low mid-IR fluxes, confirming this picture. The v sin i = 16 km s(-1) confirms that the star cannot be aligned with the outer disk, but is likely close to equator-on and to be aligned with the inner disk. This anomalous orientation is a challenge for standard theories of protoplanetary disk formation.Science & Technology Facilities Council (STFC): ST/S000399/1.
ESO fellowship.
European Union (EU): 823 823.
German Research Foundation (DFG): FOR 2634/1 TE 1024/1-1.
French National Research Agency (ANR): ANR-16-CE31-0013.
Alexander von Humboldt Foundation.
European Research Council (ERC): 678 194.
European Research Council (ERC): 742 095.
National Aeronautics & Space Administration (NASA).
National Science Foundation (NSF).
National Aeronautics & Space Administration (NASA): NNG05GF22G.
National Science Foundation (NSF): AST-0909182, AST-1 313 422
High-pressure study of the non-Fermi liquid material U_2Pt_2In
The effect of hydrostatic pressure (p<= 1.8 GPa) on the non-Fermi liquid
state of U_2Pt_2In is investigated by electrical resistivity measurements in
the temperature interval 0.3-300 K. The experiments were carried out on
single-crystals with the current along (I||c) and perpendicular (I||a) to the
tetragonal axis. The pressure effect is strongly current-direction dependent.
For I||a we observe a rapid recovery of the Fermi-liquid T^2-term with
pressure. The low-temperature resistivity can be analysed satisfactorily within
the magnetotransport theory of Rosch, which provides strong evidence for the
location of U_2Pt_2In at an antiferromagnetic quantum critical point. For I||c
the resistivity increases under pressure, indicating the enhancement of an
additional scattering mechanism. In addition, we have measured the pressure
dependence of the antiferromagnetic ordering temperature (T_N= 37.6 K) of the
related compound U_2Pd_2In. A simple Doniach-type diagram for U_2Pt_2In and
U_2Pd_2In under pressure is presented.Comment: 21 pages (including 5 figures); pdf forma
Gauged W Algebras
We perform an Hamiltonian reduction on a classical \cw(\cg, \ch) algebra, and
prove that we get another \cw(\cg, \ch) algebra, with . In
the case \cg=S\ell(n), the existence of a suitable gauge, called Generalized
Horizontal Gauge, allows to relate in this way two \cw-algebras as soon as
their corresponding \ch-algebras are related by inclusion.Comment: 11 p., Latex. There was a misprint on the last autho
Predictions from a stochastic polymer model for the MinDE dynamics in E.coli
The spatiotemporal oscillations of the Min proteins in the bacterium
Escherichia coli play an important role in cell division. A number of different
models have been proposed to explain the dynamics from the underlying
biochemistry. Here, we extend a previously described discrete polymer model
from a deterministic to a stochastic formulation. We express the stochastic
evolution of the oscillatory system as a map from the probability distribution
of maximum polymer length in one period of the oscillation to the probability
distribution of maximum polymer length half a period later and solve for the
fixed point of the map with a combined analytical and numerical technique. This
solution gives a theoretical prediction of the distributions of both lengths of
the polar MinD zones and periods of oscillations -- both of which are
experimentally measurable. The model provides an interesting example of a
stochastic hybrid system that is, in some limits, analytically tractable.Comment: 16 page
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