4,246 research outputs found
Pump- and Probe-polarization Analyses of Ultrafast Carrier Dynamics in Organic Superconductors
We investigated photo-excited carrier relaxation dynamics in the strongly correlated organic superconductors kappa-(BEDT-TTF)(2)Cu(NCS)(2) and kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br, using different polarizations of pump and probe pulses. Below the glasslike transition temperature (T (g)) anisotropic responses for probe polarization were observed in both compounds. Decomposing the data into anisotropic and isotropic components, we found the anisotropic component shows no pump polarization dependence, meaning that dissipative excitation process was dominant for the anisotropic carrier relaxation. This behavior indicates that the appearance of anisotropic responses can be associated with spatial symmetry breaking due to structural change of BEDT-TTF molecules
Proceed with caution: an economic perspective on the UK's value based pricing proposals
The shift from the Pharmaceutical Pricing Regulation Scheme to Value Based Pricing (VBP) is an important change in the way that medicines will be priced, and consequently, reimbursed in the United Kingdom. Whilst the opportunity to purchase new medicines based on value to society is one that should be welcomed, we should proceed with caution. We highlight ten issues that should be considered relating to innovation, the role and meaning of funding threshold and the adjustments to reflect burden of illness, therapeutic innovation and improvement and wider societal factors.
Most importantly, the assessment of value should continue to be based on the characteristics of the displaced activities (e.g. the health produced). To a large extent, all that is changing under VBP are the characteristics being considered; weighted health rather than unweighted health. In addition, we should not totally abandon a cost-utility framework for appraisal just because its current formulation does not match the wider perspective now desired by government
A new design of nanocrystalline silicon optical devices based on 3-dimensional photonic crystal structures
We propose a new design of nanocrystalline silicon optical devices which are based on control of electromagnetic fields, electronic states, as well as the phonon dispersion of size-controlled silicon quantum dots
Silicon nanowires for advanced sensing: Electrical and electromechanical characteristics and functionalisation technology
Nonlinear feedback oscillations in resonant tunneling through double barriers
We analyze the dynamical evolution of the resonant tunneling of an ensemble
of electrons through a double barrier in the presence of the self-consistent
potential created by the charge accumulation in the well.
The intrinsic nonlinearity of the transmission process is shown to lead to
oscillations of the stored charge and of the transmitted and reflected fluxes.
The dependence on the electrostatic feedback induced by the self-consistent
potential and on the energy width of the incident distribution is discussed.Comment: 10 pages, TeX, 5 Postscript figure
Observation of an energetic radiation burst from mountain-top thunderclouds
During thunderstorms on 2008 September 20, a simultaneous detection of gamma
rays and electrons was made at a mountain observatory in Japan located 2770 m
above sea level. Both emissions, lasting 90 seconds, were associated with
thunderclouds rather than lightning. The photon spectrum, extending to 10 MeV,
can be interpreted as consisting of bremsstrahlung gamma rays arriving from a
source which is 60 - 130 m in distance at 90% confidence level. The observed
electrons are likely to be dominated by a primary population escaping from an
acceleration region in the clouds.Comment: 12 pages, 3 figures, accepted for publication in Physical Review
Letter
Universality classes in directed sandpile models
We perform large scale numerical simulations of a directed version of the
two-state stochastic sandpile model. Numerical results show that this
stochastic model defines a new universality class with respect to the Abelian
directed sandpile. The physical origin of the different critical behavior has
to be ascribed to the presence of multiple topplings in the stochastic model.
These results provide new insights onto the long debated question of
universality in abelian and stochastic sandpiles.Comment: 5 pages, RevTex, includes 9 EPS figures. Minor english corrections.
One reference adde
A Unified Approach to Solvable Models of Dilaton Gravity in Two-Dimensions Based on Symmetry
A large class of solvable models of dilaton gravity in two space-time
dimensions, capable of describing black hole geometry, are analyzed in a
unified way as non-linear sigma models possessing a special symmetry. This
symmetry, which can be neatly formulated in the target-space-covariant manner,
allows one to decompose the non-linearly interacting dilaton-gravity system
into a free field and a field satisfying the Liouville equation with in general
non-vanishing cosmological term. In this formulation, all the existent models
are shown to fall into the category with vanishing cosmological constant.
General analysis of the space-time structureinduced by a matter shock wave is
performed and new models, with and without the cosmological term, are
discussed.Comment: 29 pages, LaTe
Update: Eliciting societal preferences for weighting QALY's according to burden of illness, size of gain and end of life
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