Tunable phonon-cavity coupling in graphene membranes

A major achievement of the past decade has been the realization of macroscopic quantum systems by exploiting interactions between optical cavities and mechanical resonators. In these systems, phonons are coherently annihilated or created in exchange for photons. Similar phenomena have recently been observed through "phonon cavity" coupling -- energy exchange between modes of a single system as mediated by intrinsic material nonlinearity. To date, this has been demonstrated primarily for bulk crystalline, high-quality-factor (Q>100,000) mechanical systems operated at cryogenic temperatures. Here we propose graphene as an ideal candidate for the study of such nonlinear mechanics. The large elastic modulus of this material and capability for spatial symmetry breaking via electrostatic forces is expected to generate a wealth of nonlinear phenomena, including tunable inter-modal coupling. We have fabricated circular graphene membranes and report strong phonon cavity effects at room temperature, despite the modest Q (~100) of this system. We observe both amplification into parametric instability ("mechanical lasing") and cooling of Brownian motion in the fundamental mode through excitation of cavity sidebands. Furthermore, we characterize quenching of these parametric effects at large vibrational amplitudes, offering a window on the all-mechanical analogue of cavity optomechanics, where observation of such effects has proven elusive

Fatos e mitos sobre imunomoduladores Facts and myths about immunomodulators

O objetivo deste artigo é discutir alguns fatos dos imunomoduladores modernos que podem ser úteis para o dermatologista clínico. Outro objetivo importante é o de dissipar mitos que possam ter impacto negativo no uso dessas drogas pelo clínico. O foco inicial está em imunomoduladores estimuladores que podem conduzir à acentuação da resposta normal das células imunocompetentes. Para tanto, diversos aspectos associados à regulação do sistema imune e às vias regulatórias das células do sistema imune são mencionados. Discutem-se a regulação aberrante e seu impacto no sistema imune e examina-se a classe de drogas imunossupressoras que têm sua função bem estabelecida. Diversas drogas não foram mencionadas. A razão para isso é o foco do artigo que pretende cobrir os fatos bem estabelecidos ou os mitos que as novas evidências científicas modificaram. Com esse padrão em mente, é provável que exista uma quantidade considerável de similaridade nos conceitos, uma vez que descrevem drogas imunomoduladoras. Nesse contexto, a intenção de fornecer novas perspectivas de como o sistema imune pode ser modulado por essas drogas supera esse problema.<br>The objective of this article is to discuss some facts of modern immunomodulators that might be useful for clinical dermatology. Moreover, it aims to dispel myths that might have a negative impact on the use of such drugs by clinicians. The primary focus is on immunomodulators that stimulate and may enhance the normal response of immunocompetent cells. Therefore, several aspects associated to immune system regulation, and regulatory pathways of immune cells are also mentioned. Furthermore, aberrant regulation is discussed in the context of immunomodulator use and the impact this has on the immune system. This review also examines the class of immunosuppressive drugs and their wellestablished function. Several drugs were not mentioned since the article focuses on well accepted facts or myths that new scientific evidences have changed. With that in mind, it is likely that there is a considerable amount of similarity in concepts, given that they describe immunomodulating drugs. In this context, the intention to provide important insight into how the immune system can be modulated by theses drugs surpasses this problem