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The visionary idea that RNA adopts nonbiological roles in today's nanomaterial world has been nothing short of phenomenal. These RNA molecules have ample chemical functionality and self-assemble to form distinct nanostructures in response to external stimuli. They may be combined with inorganic materials to produce nanomachines that carry cargo to a target site in a controlled manner and respond dynamically to environmental changes. Comparable to biological cells, programmed RNA nanomachines have the potential to replicate bone healing in vitro. Here, an RNA-biomineral nanomachine is developed, which accomplishes intrafibrillar and extrafibrillar mineralization of collagen scaffolds to mimic bone formation in vitro. Molecular dynamics simulation indicates that noncovalent hydrogen bonding provides the energy source that initiates self-assembly of these nanomachines. Incorporation of the RNA-biomineral nanomachines into collagen scaffolds in vivo creates an osteoinductive microenvironment within a bone defect that is conducive to rapid biomineralization and osteogenesis. Addition of RNA-degrading enzymes into RNA-biomineral nanomachines further creates a stop signal that inhibits unwarranted bone formation in tissues. The potential of RNA in building functional nanostructures has been underestimated in the past. The concept of RNA-biomineral nanomachines participating in physiological processes may transform the nanoscopic world of life science.
Sophisticated thin film growth techniques increasingly rely on the addition of a plasma component to open or widen a processing window, particularly at low temperatures. However, the addition of the plasma into the growth environment also complicates the surface dynamical evolution. Taking advantage of continued increases in accelerator-based X-ray source brilliance, this real-time study uses X-ray Photon Correlation Spectroscopy (XPCS) to elucidate the nanoscale surface dynamics during Plasma-Enhanced Atomic Layer Deposition (PE-ALD) of an epitaxial indium nitride film. XPCS examines the evolution of the coherent X-ray scattering speckle pattern, which is a fingerprint of the unique sample microstructure at each moment in time. In PE-ALD, ultrathin films are synthesized from repeated cycles of alternating self-limited surface reactions induced by temporally-separated pulses of material precursor and plasma reactant, allowing the influence of each on the evolving morphology to be examined. During the heteroepitaxial 3D growth examined here, sudden changes in surface structure during initial film growth, consistent with numerous overlapping stress-relief events, are observed. When the film becomes continuous, the nanoscale surface morphology abruptly becomes long-lived with correlation time spanning the period of the experiment. Throughout the growth experiment, there is a consistent repeating pattern of correlations associated with the cyclic growth process, which is modeled as transitions between different surface states. The plasma exposure does not simply freeze in a structure that is then built upon in subsequent cycles, but rather there is considerable surface evolution during all phases of the growth cycle.
Chemically bonded aluminum phosphate coating modified with Al2O3-MWCNTs was prepared for anti-corrosion in high-temperature marine environment. a-Al2O3 was successfully and conveniently coupled to the multi-walled carbon nanotubes by surface modification. Then the hybrid materials mixed with coating materials were applied on heat-resistant steel using high-pressure airless spraying. SEM, XRD, FT-IR spectrum, Raman spectrum and TGA were performed to prove the success of hybridization. Simultaneously, adhesion, electrochemical, and SEM experiments were conducted to characterize the protective performance of the coating under different ablation times. One noteworthy phenomenon showed by the thermogravimetric analysis results is that the initial decomposition temperature of Al2O3-MWCNTs was increased by 100 °C compared with pure MWCNTs, which provided a basis for the application of the ceramic coatings in oxidation-resistant environment at 600 °C. The results of adhesion experiments showed that the dry bonding force of the ceramic coating with Al2O3-MWCNTs added on the substrate /coating interface was 3 times higher than that of the pure coating. By adding Al2O3-MWCNTs, the coating had a denser mosaic structure on the outside a three-dimensional mesh structure on the inside, which provided outstanding shielding properties and more electron channels, and had the best surface quality after ablation at 600 ℃. Additionally, the Rct value was 34.7 kΩ/cm2 after 100 h of high temperature ablation, which is 345 times of that without added coating. In general, the results showed that the corrosion resistance of the coating with Al2O3-MWCNTs as the reinforcing phase was still maintained at a high level.
Ultrathin nanosheets (F-MnCo) with a thickness of ~1.7 nm are synthesized by incubation of NaF, Co(CH 3 COO) 2 , and KMnO 4 in aqueous solution at room temperature. F-MnCo is comprised of the self-assembled CoOOH and Co(OH)F nanocrystals and highly dispersed MnO 2 . Through the calcination at 230 °C, CoOOH and Co(OH)F are pyrolyzed to form F-Co 3 O 4 , with manganese being concomitantly embedded in the lattice of F-Co 3 O 4 . The synthesized F-Mn x Co 3-x O 4 is a solid solution, exhibiting a structure of ultrathin nanosheets with a thickness of ~1.1 nm. F-Mn x Co 3-x O 4 has been applied as catalyst for the oxidations of 5-hydroxymethyl furfural (HMF) and alcohols, exhibiting an excellent catalytic activity and a high aldehyde selectivity. The ultrathin nanosheets can facilitate mass transfer of reactants and provide more open active sites. High proportion of surface lattice oxygen, abundant oxygen vacancy, excellent oxygen mobility, and uniformly embedded manganese in the lattice also contribute to F-Mn x Co 3-x O 4 exhibiting the excellent catalytic activity.
Incorporation of base metals to carbon supported Pt catalysts is known to enhance oxygen reduction reaction (ORR) activity. Therefore, Pt-base metals random alloys, such as Pt-Co, are often applied as cathode catalysts in proton exchange membrane fuel cells (PEMFCs). However, poor stability of Co under oxidative and acidic conditions makes the enhancement limited during long-term fuel cell testing. Recently, we have developed a robust method to prepare L1 0 ordered CoPt catalysts that exhibit superior fuel cell performances compared with the random alloy counterpart. In this systematic study, we observed that carbon supports impose strong effects not only on the growth of CoPt L1 0 intermetallic nanoparticles but also on the fuel cell performances. Solid carbons, including Vulcan other highly graphitized carbons, have moderate surface areas and relatively higher degree of graphitization. CoPt L1 0 intermetallic particles prepared such type of carbons usually have a large size distribution. But their fuel cell performances are still desirable, showing high current densities at low voltages and less carbon corrosion. Moreover, we found that surface functionalization can improve the size distribution and dispersion of nanoparticles, thus improving the fuel cell performances. In parallel, porous carbons of high surface areas were also applied as the supports for depositing CoPt L1 0 intermetallic nanoparticles. Different from the particles on surface of solid carbons, a large number of nanoparticles are located in the micropores of porous carbons. These nanoparticles can maintain their small particle size and a narrow size distribution after heat treatment. CoPt L1 0 intermetallic nanoparticles on porous supports exhibit excellent performances at high voltage end in fuel cell testing.
Sub-harmonic oscillation is a well-known problem in DC/DC converters with current mode control. To avoid this problem, a method to achieve adjustable-slope compensation is proposed. This method makes the compensating ramp slope appropriate for various output voltage levels. Besides solving the sub-harmonic oscillation problem, this method can also make the system respond better due to the alleviation of the over-compensation found in the traditional method, especially at low output voltage levels. Furthermore, power-saving in the current sensor is one other advantage because only the initial inductor current value in every cycle is needed. This can improve efficiency in current mode control, which is inherently lower than voltage mode control. An integrated circuit implementation of a current mode buck converter with the proposed method was made with a standard 0.35-mum CMOS process
Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text C. Wang, M. Chen, and Z. Meng, "Phase Noise Reduction of a Compact Brillouin/Erbium Fiber Laser," in Asia Pacific Optical Sensors Conference, OSA Technical Digest (online) (Optica Publishing Group, 2016), paper JF2A.6. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article
To reduce the risk of atherosclerotic disease, it is necessary to not only diagnose the presence of atherosclerotic plaques but also assess the vulnerability risk of plaques. Accurate detection of the reactive oxygen species (ROS) level at plaque sites represents a reliable way to assess the plaque vulnerability. Herein, through a simple one-pot reaction, two near-infrared (NIR) fluorescent dyes, one is ROS responsive and the other is inert to ROS, are coassembled in an amphiphilic amino acid-assembled nanoparticle. In the prepared NIR fluorescent amino acid nanoparticle (named FANP), the fluorescent properties and ROS-responsive behaviors of the two fluorescent dyes are well maintained. Surface camouflage through red blood cell membrane (RBCM) encapsulation endows the finally obtained FANP@RBCM nanoprobe with not only further reduced cytotoxicity and improved biocompatibility but also increased immune escape capability, prolonged blood circulation time, and thus enhanced accumulation at atherosclerotic plaque sites. In vitro and in vivo experiments demonstrate that FANP@RBCM not only works well in probing the occurrence of atherosclerotic plaques but also enables plaque vulnerability assessment through the accurate detection of the ROS level at plaque sites in a reliable ratiometric mode, thereby holding great promise as a versatile tool for the diagnosis and risk assessment of atherosclerotic disease.
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