Electromagnetically induced transparency (EIT) [1,2] provides a powerful mechanism for controlling light propagation in a dielectric medium, and for producing slow and fast light. EIT traditionally arises from destructive interference induced by a nonradiative coherence in an atomic system. Stimulated Brillouin scattering (SBS) of light from propagating hypersonic acoustic waves [3] has also been used successfully for the generation of slow and fast light [4][5][6][7]. However, EIT-type processes based on SBS were considered infeasible because of the short coherence lifetime of hypersonic phonons. Here, we report a new Brillouin scattering induced transparency (BSIT) phenomenon generated by acousto-optic interaction of light with long-lived propagating phonons [8,9]. We demonstrate that BSIT is uniquely non-reciprocal due to the propagating acoustic phonon wave and accompanying momentum conservation requirement. Using a silica microresonator having naturally occurring forward-SBS phasematched modal configuration [8,9], we show that BSIT enables compact and ultralow-power slow-light generation with delay-bandwidth product comparable to state-of-the-art SBS systems. [3,10,11] is a fundamental materiallevel nonlinearity occurring in all states of matter [12] in which two optical fields are coupled to a traveling acoustic wave through photoelastic scattering and electrostriction. The light fields scatter from the periodic photoelastic perturbation generated by the traveling acoustic wave, while simultaneously writing a spatiotemporally beating electrostriction force whose momentum and frequency matches the acoustic wave. Phase matching for SBS is thus defined by both 1 arXiv:1408.1739v2 [physics.optics] 11 Aug 2014 energy and momentum conservation, and is satisfied in back-scattering only by multi-GHz phonon modes in most solids. SBS is frequently used for optical gain [3,13], laser linewidth narrowing [14], optical phase conjugation [15], dynamic gratings [16], and even material characterization and microscopy [17][18][19][20][21][22]. The applications of SBS in superluminal and slow light experiments have been recognized as well [4][5][6][7]. However, unlike the case of electromagnetically induced transparency (EIT) [1,2], the generation of transparency with SBS has never been demonstrated. This is because in typical Brillouin scattering pump-probe systems the lifetimes of phonons at multi-GHz frequencies are much shorter than the photon lifetimes [3,23,24], effectively disabling the coherent interference of probe Stokes scattering and pump anti-Stokes scattering pathways. In a forward-scattering SBS system however, this lifetime relationship can be reversed by coupling the light fields through a low-frequency long-lived phonon mode as shown recently in the experimental demonstration of forward-SBS lasing [8] and Brillouin cooling [9]. Stimulated Brillouin scattering (SBS)Nonlinear optical processes such as EIT need to satisfy the energy-momentum conservation, leading to the phase-matching requirement. For...

Transforming growth factor-β (TGF-β) is a potent anti-inflammatory cytokine that regulates interleukin-1 receptor and Toll-like receptor (TLR) signalling. Here we show a novel mechanism where TGF-β1-induced K48-linked polyubiquitination and degradation of the adaptor myD88 protein is dependent on the smad6 protein, but not smad7, and mediated by recruitment of the smad ubiquitin regulator factor proteins, smurf1 and smurf2, which have E3-ubiquitin ligase activity. smurf1 interaction with myD88 appears to be mediated by smad6, and smurf2 interaction by smurf1. Knockdown of endogenous smurf1 or smurf2 by RnA interference significantly suppresses the anti-inflammatory effects of TGF-β1 by preventing lipopolysaccharide-induced nF-κB nuclear translocation, resulting in de-suppression of proinflammatory gene expression. similar effects are observed on the lipoteichoic-acid-induced TLR2 pathway, which is also myD88-dependent, but not the myD88-independent TLR3 pathway. Thus, our results suggest that myD88 degradation driven by the smad6-smurf pathway is a novel mechanism for TGF-β1-mediated negative regulation of myD88-dependent pro-inflammatory signalling.

Although the ubiquitin-editing enzyme A20 is a key player in inflammation and autoimmunity, its role in cancer metastasis remains unknown. Here we show that A20 monoubiquitylates Snail1 at three lysine residues and thereby promotes metastasis of aggressive basal-like breast cancers. A20 is significantly upregulated in human basal-like breast cancers and its expression level is inversely correlated with metastasis-free patient survival. A20 facilitates TGF-β1-induced epithelial-mesenchymal transition (EMT) of breast cancer cells through multi-monoubiquitylation of Snail1. Monoubiquitylated Snail1 has reduced affinity for glycogen synthase kinase 3β (GSK3β), and is thus stabilized in the nucleus through decreased phosphorylation. Knockdown of A20 or overexpression of Snail1 with mutation of the monoubiquitylated lysine residues into arginine abolishes lung metastasis in mouse xenograft and orthotopic breast cancer models, indicating that A20 and monoubiquitylated Snail1 are required for metastasis. Our findings uncover an essential role of the A20-Snail1 axis in TGF-β1-induced EMT and metastasis of basal-like breast cancers.

A two-step metal assisted chemical etching technique is used to systematically vary the sidewall roughness of Si nanowires in vertically aligned arrays. The thermal conductivities of nanowire arrays are studied using time domain thermoreflectance and compared to their high-resolution transmission electron microscopy determined roughness. The thermal conductivity of nanowires with small roughness is close to a theoretical prediction based on an upper limit of the mean-free-paths of phonons given by the nanowire diameter. The thermal conductivity of nanowires with large roughness is found to be significantly below this prediction. Raman spectroscopy reveals that nanowires with large roughness also display significant broadening of the one-phonon peak; the broadening correlates well with the reduction in thermal conductivity. The origin of this broadening is not yet understood, as it is inconsistent with phonon confinement models, but could derive from microstructural changes that affect both the optical phonons observed in Raman scattering and the acoustic phonons that are important for heat conduction. V

It is commonly accepted that brain phospholipids are highly enriched with long-chain polyunsaturated fatty acids (PUFAs). However, the evidence for this remains unclear. We used HPLC-MS to analyze the content and composition of phospholipids in rat brain and compared it to the heart, kidney, and liver. Phospholipids typically contain one PUFA, such as 18:2, 20:4, or 22:6, and one saturated fatty acid, such as 16:0 or 18:0. However, we found that brain phospholipids containing monounsaturated fatty acids in the place of PUFAs are highly elevated compared to phospholipids in the heart, kidney, and liver. The relative content of phospholipid containing PUFAs is ~ 60% in the brain, whereas it is over 90% in other tissues. The most abundant species of phosphatidylcholine (PC) is PC(16:0/18:1) in the brain, whereas PC(18:0/20:4) and PC(16:0/20:4) are predominated in other tissues. Moreover, several major species of plasmanyl and plasmenyl phosphatidylethanolamine are found to contain monounsaturated fatty acid in the brain only. Overall, our data clearly show that brain phospholipids are the least enriched with PUFAs of the four major organs, challenging the common belief that the brain is highly enriched with PUFAs.