2,247 research outputs found
Roadmap on optical rogue waves and extreme events
The pioneering paper 'Optical rogue waves' by Solli et al (2007 Nature 450 1054) started the new subfield in optics. This work launched a great deal of activity on this novel subject. As a result, the initial concept has expanded and has been enriched by new ideas. Various approaches have been suggested since then. A fresh look at the older results and new discoveries has been undertaken, stimulated by the concept of 'optical rogue waves'. Presently, there may not by a unique view on how this new scientific term should be used and developed. There is nothing surprising when the opinion of the experts diverge in any new field of research. After all, rogue waves may appear for a multiplicity of reasons and not necessarily only in optical fibers and not only in the process of supercontinuum generation. We know by now that rogue waves may be generated by lasers, appear in wide aperture cavities, in plasmas and in a variety of other optical systems. Theorists, in turn, have suggested many other situations when rogue waves may be observed. The strict definition of a rogue wave is still an open question. For example, it has been suggested that it is defined as 'an optical pulse whose amplitude or intensity is much higher than that of the surrounding pulses'. This definition (as suggested by a peer reviewer) is clear at the intuitive level and can be easily extended to the case of spatial beams although additional clarifications are still needed. An extended definition has been presented earlier by N Akhmediev and E Pelinovsky (2010 Eur. Phys. J. Spec. Top. 185 1-4). Discussions along these lines are always useful and all new approaches stimulate research and encourage discoveries of new phenomena. Despite the potentially existing disagreements, the scientific terms 'optical rogue waves' and 'extreme events' do exist. Therefore coordination of our efforts in either unifying the concept or in introducing alternative definitions must be continued. From this point of view, a number of the scientists who work in this area of research have come together to present their research in a single review article that will greatly benefit all interested parties of this research direction. Whether the authors of this 'roadmap' have similar views or different from the original concept, the potential reader of the review will enrich their knowledge by encountering most of the existing views on the subject. Previously, a special issue on optical rogue waves (2013 J. Opt. 15 060201) was successful in achieving this goal but over two years have passed and more material has been published in this quickly emerging subject. Thus, it is time for a roadmap that may stimulate and encourage further research.Peer ReviewedPostprint (author's final draft
UNITY CONSCIOUSNESS: A QUANTUM BIOMECHANICAL FOUNDATION
Citing research in consciousness, quantum physics, biophysics and cosmology, we propose the collective amplification of quantum effects as the basis for scientifically describing Kundalini awakening, and the higher-order, emergent phenomenon of Unity consciousness, Such alterations of consciousness have their origin in quantum-scale processes, such as self-induced transparency, superradiance, superpositions, quantum tunneling, and Bose-Einstein condensation, Microtubules are considered to be key components in non-local, quantum processes critical to human consciousness, We postulate that bundles of fibers (neural cells), each containing numerous microtubule "lasers" acting in unison, collectively result in a massive surge of light energy to the brain, The sudden onset and radically altered nature of such states are consistent with a model based on the activation of a laser. The liquid crystalline nature of the human body likely provides a foundation for the non-local aspect ofVniry consciousness, The unifYing paradigm of the "quantum hologram" is introduced ro apply quantum properties to macroscopic events
Fast Radio Bursts
The discovery of radio pulsars over a half century ago was a seminal moment
in astronomy. It demonstrated the existence of neutron stars, gave a powerful
observational tool to study them, and has allowed us to probe strong gravity,
dense matter, and the interstellar medium. More recently, pulsar surveys have
led to the serendipitous discovery of fast radio bursts (FRBs). While FRBs
appear similar to the individual pulses from pulsars, their large dispersive
delays suggest that they originate from far outside the Milky Way and hence are
many orders-of-magnitude more luminous. While most FRBs appear to be one-off,
perhaps cataclysmic events, two sources are now known to repeat and thus
clearly have a longer-lived central engine. Beyond understanding how they are
created, there is also the prospect of using FRBs -- as with pulsars -- to
probe the extremes of the Universe as well as the otherwise invisible
intervening medium. Such studies will be aided by the high implied all-sky
event rate: there is a detectable FRB roughly once every minute occurring
somewhere on the sky. The fact that less than a hundred FRB sources have been
discovered in the last decade is largely due to the small fields-of-view of
current radio telescopes. A new generation of wide-field instruments is now
coming online, however, and these will be capable of detecting multiple FRBs
per day. We are thus on the brink of further breakthroughs in the
short-duration radio transient phase space, which will be critical for
differentiating between the many proposed theories for the origin of FRBs. In
this review, we give an observational and theoretical introduction at a level
that is accessible to astronomers entering the field.Comment: Invited review article for The Astronomy and Astrophysics Revie
Phononics: Manipulating heat flow with electronic analogs and beyond
The form of energy termed heat that typically derives from lattice
vibrations, i.e. the phonons, is usually considered as waste energy and,
moreover, deleterious to information processing. However, with this colloquium,
we attempt to rebut this common view: By use of tailored models we demonstrate
that phonons can be manipulated like electrons and photons can, thus enabling
controlled heat transport. Moreover, we explain that phonons can be put to
beneficial use to carry and process information. In a first part we present
ways to control heat transport and how to process information for physical
systems which are driven by a temperature bias. Particularly, we put forward
the toolkit of familiar electronic analogs for exercising phononics; i.e.
phononic devices which act as thermal diodes, thermal transistors, thermal
logic gates and thermal memories, etc.. These concepts are then put to work to
transport, control and rectify heat in physical realistic nanosystems by
devising practical designs of hybrid nanostructures that permit the operation
of functional phononic devices and, as well, report first experimental
realizations. Next, we discuss yet richer possibilities to manipulate heat flow
by use of time varying thermal bath temperatures or various other external
fields. These give rise to a plenty of intriguing phononic nonequilibrium
phenomena as for example the directed shuttling of heat, a geometrical phase
induced heat pumping, or the phonon Hall effect, that all may find its way into
operation with electronic analogs.Comment: 24 pages, 16 figures, modified title and revised, accepted for
publication in Rev. Mod. Phy
Electrochemical oxidation of H 2, CO gas mixtures in polymer-electrolyte-membrane fuel cells
Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2014von Sebastian Kirsc
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