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<p class="MsoNormal">There will be two John Anderson Colloquia next week, the first is by visiting professor Katarina Lorenz (Lisbon) and the second will be by Daniel Stein (NYU). As usual, there will be tea/coffee served after the colloquia.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Speaker: Prof Katarina Lorenz (IPFN, IST, Universidade de Lisboa, Portugal, Visiting Professor University of Strathclyde)<o:p></o:p></p>
<p class="MsoNormal">Time/Date: 3pm Wednesday 21/1/2015<o:p></o:p></p>
<p class="MsoNormal">Room: JA3.14<o:p></o:p></p>
<p class="MsoNormal">Title: Towards efficient solid state lighting using ion beam techniques<o:p></o:p></p>
<p class="MsoNormal">Abstract:<o:p></o:p></p>
<p class="MsoNormal">Current commercial “white LEDs” are based on blue-emitting InGaN LEDs coupled to a yellow-emitting phosphor. The efficiency of these phosphor conversion LEDs is limited by energy losses inherent to the absorption and emission processes.
The alternative approach of combining three (blue-, green- and red-emitting) LEDs promises to be more efficient and more versatile. However, the internal quantum efficiency (IQE) for nitride-based LEDs decreases dramatically in the green and red spectral region.
Theoretical work suggests that InGaN/GaN quantum wells with graded compositional profiles may increase IQE and mitigate Auger losses when compared to conventional, abrupt QWs. In this work we investigate the possibility of quantum well intermixing to achieve
such graded layers. A combination of ion irradiation and thermal annealing can promote the interdiffusion of InGaN QWs and GaN barrier layers. Another approach to achieve long wavelength emission from III-nitride devices is the doping with optically active
rare earth ions. A review on recent advances of rare earth implantation in GaN layers and nanostructures will be presented.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Speaker: Prof Daniel Stein (Physics and Mathematics, NYU)<o:p></o:p></p>
<p class="MsoNormal">Time/Date: 3pm Thursday 22/1/2015<o:p></o:p></p>
<p class="MsoNormal">Room: JA3.14<o:p></o:p></p>
<p class="MsoNormal">Title: Order, Disorder, Symmetry and Complexity<o:p></o:p></p>
<p class="MsoNormal">Abstract:<o:p></o:p></p>
<p class="MsoNormal">One of the deepest scientific questions we can ask is, How might complexity arise? That is, starting from simple, undirected processes subject to physical and chemical laws, how could structures with complex shapes and patterns arise, and
even more perplexing, what processes could give rise to living cells, and how might they then organize themselves into complex organisms, leading ultimately to such things as brains, consciousness, and societies?<o:p></o:p></p>
<p class="MsoNormal">We are far from answering these questions at almost any level, but they have attracted increasing attention in the scientific community, and some initial headway has been made. The basic problem can be reframed as one involving the self-organization
of microscopic constituents into larger assemblies, in such a way that the process leads to an increase of information, the creation of new patterns, and eventually increasing hierarchical levels of complex structure. The key to understanding these processes
cannot be found in any single (natural or social) scientific field but rather in collaborations that cross many disciplinary boundaries.<o:p></o:p></p>
<p class="MsoNormal">Although we are still at the initial stages of inquiry, new and interesting approaches and points of view have arisen. In this talk I present one that arises from the point of view of physics. We start by describing the (well-understood)
phenomenon of matter organizing itself into simple ordered structures, like crystals and magnets, and then explore how our ideas are affected when we consider the effects of randomness and disorder, pervasive in the physical world, and focusing in particular
on glasses and spin glasses. We will see that randomness and disorder are, paradoxically, essential for more ordered, complex structures to arise. Using these ideas, we provide some hints (but only hints) as to how we can gain a handle on issues related to
the increase of complexity. Underlying all of our considerations is the notion of symmetry in physics: where it comes from and how matter "breaks" its inherent symmetry to create new information and ever-increasing complexity.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">http://www.strath.ac.uk/physics/research/colloquia/<o:p></o:p></p>
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