This study demonstrates that the thermally induced collapse of end-grafted poly(N-isopropylacrylamide) (PNIPAM) above the lower critical solution temperature (LCST) of 32 degrees C depends on the chain grafting density and molecular weight. The polymer was grafted from the surface of a self-assembled monolayer containing the initiator (BrC(CH3)2COO(CH2)11S)2, using surface-initiated atom transfer radical polymerization. Varying the reaction time and monomer concentration controlled the molecular weight, and diluting the initiator in the monolayer altered the grafting density. Surface force measurements of the polymer films showed that the chain collapse above the LCST decreases with decreasing grafting density and molecular weight. At T > LCST, the advancing water contact angle increases sharply on PNIPAM films of high molecular weight and grafting density, but the change is less pronounced with films of low-molecular-weight chains at lower densities. Below the LCST, the force-distance profiles exhibit nonideal polymer behavior and suggest that the brush architecture comprises dilute outer chains and much denser chains adjacent to the surface.

Long noncoding RNAs (lncRNAs) modulate various biological processes, but their role in host antiviral responses is largely unknown. Here we identify a lncRNA as a key regulator of antiviral innate immunity. Following from the observation that a lncRNA that we call negative regulator of antiviral response (NRAV) was dramatically downregulated during infection with several viruses, we ectopically expressed NRAV in human cells or transgenic mice and found that it significantly promotes influenza A virus (IAV) replication and virulence. Conversely, silencing NRAV suppressed IAV replication and virus production, suggesting that reduction of NRAV is part of the host antiviral innate immune response to virus infection. NRAV negatively regulates the initial transcription of multiple critical interferon-stimulated genes (ISGs), including IFITM3 and MxA, by affecting histone modification of these genes. Our results provide evidence for a lncRNA in modulating the antiviral interferon response.

Magnetorheological fluid technology has gained significant development during the past decades. The application of magnetorheological fluids has grown rapidly in civil engineering, safety engineering, transportation, and life science with the development of magnetorheological fluid–based devices, especially magnetorheological fluid dampers. The magnetorheological fluid dampers could offer an outstanding capability in semiactive vibration control due to excellent dynamical features such as fast response, environmentally robust characteristics, large force capacity, low power consumption, and simple interfaces between electronic input and mechanical output. To address the fast growing demand on magnetorheological fluid damping technology in extensive engineering practices, the state-of-the-art development is presented in this article, which provides a comprehensive review on the structure design and its analysis of magnetorheological fluid dampers (or systems). This can be regarded as a useful complement to several existing reviews in the recent literature on magnetorheological fluids technology, magnetorheological fluid applications, modeling of magnetorheological fluids and dampers, control strategies of magnetorheological fluid systems, and so on. The review begins with an introduction of the basic features and relevant applications of magnetorheological fluids. Then several basic structure design issues of magnetorheological fluid dampers are introduced. Following this, typical magnetorheological dampers are discussed according to the arrangement configurations of magnetorheological fluid cylinders and magnetorheological fluid control valves. Furthermore, reinforced structure designs of magnetorheological fluid dampers are provided, which focus on coil configuration, fluid resistance channel design, and electromagnetic design. Thereafter, design issues of magnetorheological fluid damper systems are discussed, which involves sensor-based magnetorheological fluid damper systems, self-powered magnetorheological fluid damper systems, fail-safe magnetorheological fluid damper systems, and integrated spring magnetorheological fluid damper systems. Importantly, to have a systematic quantitative viewpoint of the analysis and design of magnetorheological fluid dampers, the review ends with a summary of performance analysis issues, including performance specification, analytical modeling, parameter optimization, and so on.

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To fabricate a photonic crystal with large and complete photonic bandgap, it often requires backfilling of high index inorganic materials into a 3D polymer template. However, the pore network may become disconnected before the template is completely filled in a conformal coating process, which, therefore, limits the achievable maximum bandgap in the 3D photonic crystals. Here, we demonstrate nearly complete filling of the holographically patterned, diamond-like polymer templates with titania sol-gel through the electrodeposition method. The deposition proceeded in two stages: a thin titania seed layer (∼55 nm thick) was conformally coated on the surface of the polymer template at the early stage of electrodeposition, after which the deposition occurred preferentially from the template bottom layer at a rate of ∼0.4 µm/ min. After preannealing and a slow ramping rate to 500 °C to remove the polymer template, an inverse 3D anatase titania crystal was obtained without pattern collapse. The measurement of film reflectivity in the [111] direction before and after the deposition in comparison to the calculated photonic bandgap properties suggested that (1) the template was nearly completely filled by the electrodeposition process and (2) the photonic structure was well-preserved after the removal of the template.

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We present a quantitative study of the distortion from a threeterm diamond-like structure fabricated in SU8 polymer by four-beam holographic lithography. In the study of the refraction effect, theory suggests that the lattice in SU8 should be elongated in the [111] direction but have no distortion in the (111) plane, and each triangular-like hole array in the (111) plane would rotate by ~30 degrees away from that in air. Our experiments agree with the prediction on the periodicity in the (111) plane and the rotation due to refraction effect, however, we find that the film shrinkage during lithographic process has nearly compensated the predicted elongation in the [111] direction. In study of photonic bandgap (PBG) properties of silicon photonic crystals templated by the SU8 structure, we find that the distortion has decreased quality of PBG.