5,623 research outputs found
Static and non-static quantum effects in two-dimensional dilaton gravity
We study backreaction effects in two-dimensional dilaton gravity. The
backreaction comes from an term which is a part of the one-loop effective
action arising from massive scalar field quantization in a certain
approximation. The peculiarity of this term is that it does not contribute to
the Hawking radiation of the classical black hole solution of the field
equations. In the static case we examine the horizon and the physical
singularity of the new black hole solutions. Studying the possibility of time
dependence we see the generation of a new singularity. The particular solution
found still has the structure of a black hole, indicating that non-thermal
effects cannot lead, at least in this approximation, to black hole evaporation.Comment: 10 pages, no figure
Cosmological inflation driven by holonomy corrections of loop quantum cosmology
At the level of heuristic effective dynamics, we investigate the cosmological
inflation with holonomy corrections of loop quantum cosmology (LQC) in the
Friedmann-Robertson-Walker model with a single inflaton field subject to
a simple potential. In the symmetric bouncing scenario of LQC, the condition
for occurrence of the quantum bounce naturally and uniquely fixes the initial
conditions at the bouncing epoch. Around the quantum bounce, the universe
undergoes a short super-inflationary phase, which drives the inflaton field to
its potential hill and thus sets the proper initial conditions for the standard
slow-roll inflation. Between the super-inflation and the standard inflation,
there is a non-inflationary phase, which violates the slow-roll condition. The
violation of slow roll is expected to give some suppression on the low angular
power spectrum of the cosmic microwave background and different orders of
holonomy corrections shall yield different suppressions.Comment: 7 pages, 2 figures, 1 table; one reference added
Photothermal nanoblade for patterned cell membrane cutting.
We report a photothermal nanoblade that utilizes a metallic nanostructure to harvest short laser pulse energy and convert it into a highly localized and specifically shaped explosive vapor bubble. Rapid bubble expansion and collapse punctures a lightly-contacting cell membrane via high-speed fluidic flows and induced transient shear stress. The membrane cutting pattern is controlled by the metallic nanostructure configuration, laser pulse polarization, and energy. Highly controllable, sub-micron sized circular hole pairs to half moon-like, or cat-door shaped, membrane cuts were realized in glutaraldehyde treated HeLa cells
Loop Quantum Cosmology in Bianchi Type I Models: Analytical Investigation
The comprehensive formulation for loop quantum cosmology in the spatially
flat, isotropic model was recently constructed. In this paper, the methods are
extended to the anisotropic Bianchi I cosmology. Both the precursor and the
improved strategies are applied and the expected results are established: (i)
the scalar field again serves as an internal clock and is treated as emergent
time; (ii) the total Hamiltonian constraint is derived by imposing the
fundamental discreteness and gives the evolution as a difference equation; and
(iii) the physical Hilbert space, Dirac observables and semi-classical states
are constructed rigorously. It is also shown that the state in the kinematical
Hilbert space associated with the classical singularity is decoupled in the
difference evolution equation, indicating that the big bounce may take place
when any of the area scales undergoes the vanishing behavior. The investigation
affirms the robustness of the framework used in the isotropic model by
enlarging its domain of validity and provides foundations to conduct the
detailed numerical analysis.Comment: 53 pages, 2 figures; more typos corrected; HyperTeX enable
Image patterned molecular delivery into live cells using gold particle coated substrates.
An image-patterned molecular delivery system for mammalian cells is demonstrated by pulsed laser irradiation of gold particles immobilized on a substrate below a cell monolayer. Patterned cavitation bubble nucleation was captured using a time-resolved imaging system and molecular delivery verified by observing the uptake of a membrane-impermeable fluorescent dye, calcein. Delivery efficiency as high as 90% was observed and multiplexed, patterned dye delivery was demonstrated
Variability and uncertainty in empirical ground-motion prediction for probabilistic hazard and risk analyses
© The Author(s) 2015.The terms aleatory variability and epistemic uncertainty mean different things to people who routinely use them within the fields of seismic hazard and risk analysis. This state is not helped by the repetition of loosely framed generic definitions that actually inaccurate. The present paper takes a closer look at the components of total uncertainty that contribute to ground-motion modelling in hazard and risk applications. The sources and nature of uncertainty are discussed and it is shown that the common approach to deciding what should be included within hazard and risk integrals and what should be pushed into logic tree formulations warrants reconsideration. In addition, it is shown that current approaches to the generation of random fields of ground motions for spatial risk analyses are incorrect and a more appropriate framework is presented
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