33 research outputs found
Beam shaping using genetically optimized two-dimensional photonic crystals
We propose the use of two-dimensional photonic crystals with engineered
defects for the generation of an arbitrary-profile beam from a focused input
beam. The cylindrical harmonics expansion of complex-source beams is derived
and used to compute the scattered wavefunction of a 2D photonic crystal via the
multiple scattering method. The beam shaping problem is then solved using a
genetic algorithm. We illustrate our procedure by generating different orders
of Hermite-Gauss profiles, while maintaining reasonable losses and tolerance to
variations in the input beam and the slab refractive index
Psychopolitics: Peter Sedgwickâs legacy for mental health movements
This paper re-considers the relevance of Peter Sedgwick's Psychopolitics (1982) for a politics of mental health. Psychopolitics offered an indictment of âanti-psychiatryâ the failure of which, Sedgwick argued, lay in its deconstruction of the category of âmental illnessâ, a gesture that resulted in a politics of nihilism. âThe radical who is only a radical nihilistâ, Sedgwick observed, âis for all practical purposes the most adamant of conservativesâ. Sedgwick argued, rather, that the concept of âmental illnessâ could be a truly critical concept if it was deployed âto make demands upon the health service facilities of the society in which we liveâ. The paper contextualizes Psychopolitics within the âcrisis tendenciesâ of its time, surveying the shifting welfare landscape of the subsequent 25 years alongside Sedgwick's continuing relevance. It considers the dilemma that the discourse of âmental illnessâ â Sedgwick's critical concept â has fallen out of favour with radical mental health movements yet remains paradigmatic within psychiatry itself. Finally, the paper endorses a contemporary perspective that, while necessarily updating Psychopolitics, remains nonetheless âSedgwickianâ
Sociedade e conhecimento: novas tecnologias e desafios para a produção de conhecimento nas ciĂȘncias sociais
Glycosaminoglycans in ageing rat brain and in cerebral cortex from Alzheimer-type dements
The phenomenon of "pe-ischaemic conditioning" in the brain only partly involves the NMDA receptor: A magnetic resonance study
We have investigated in more detail our previous observations on a form of ischaemic pre-conditioning "metabolic adaptation", i.e.-that sequential metabolic insults (hypoxia followed 40 min later by combined hypoxia + hypoglycaemia, or vice versa) are less injurious (monitored by increased [Ca 2+] i and decreased PCr) than the immediate combined insult. We have now observed that the "adaptation" occurs between 10 and 20 min. Pre-treatment of the tissues with 10 ĂÂŒM-MK801 showed that it had no effect on the increase in [Ca 2+] i caused by the sequential insult and only partially blocked the increase observed by exposure to the immediate combined insult. Exposure to both the delayed and immediate combined insults with low extracellular Ca 2+ resulted in a two-fold increase in [Ca 2+] i , similar to the increase observed with normal extracellular Ca 2+ in the presence of MK801. The results are discussed in terms of the possible origins of the increases in [Ca 2+] i