关键词： Phase synchronization   Collective phenomenon   Mechanical oscillators   Anti-synchronization  

摘要： Phase synchronization refers to a kind of collective phenomenon that the phase difference between two or more systems is locked, and it has widely been investigated between systems with the identical physical properties, such as the synchronization between mechanical oscillators and the synchronization between atomic ensembles. Here, we investigate the synchronization behavior between the mechanical oscillator and the atomic ensemble, the systems with different physical properties, and observe a novel synchronization phenomenon, i.e., the phase sum, instead of phase difference, is locked. We refer to this distinct synchronization as the phase anti-synchronization and show that the phase anti-synchronization can be achieved in both the classical and quantum level, which means this novel collective behavior can be tested in experiment. Also, some interesting connections between phase anti-synchronization and quantum correlation are found.

关键词： Cell biology   Neuroscience  

摘要： Neurons maintain axonal homeostasis via employing a unique organization of the microtubule (MT) cytoskeleton, which supports axonal morphology and provides tracks for intracellular transport. Abnormal MT-based trafficking hallmarks the pathology of neurodegenerative diseases, but the exact mechanism regulating MT dynamics in axons remains enigmatic. Here we report on a regulation of MT dynamics by AuTophaGy(ATG)-related proteins, which previously have been linked to the autophagy pathway. We find that ATG proteins required for LC3 lipid conjugation are dispensable for survival of excitatory neurons and instead regulate MT stability via controlling the abundance of the MT-binding protein CLASP2. This function of ATGs is independent of their role in autophagy and requires the active zone protein ELKS1. Our results highlight a non-canonical role of ATG proteins in neurons and suggest that pharmacological activation of autophagy may not only promote the degradation of cytoplasmic material, but also impair axonal integrity via altering MT stability.

关键词： Carbon nanotube   non-covalent functionalisation   biomolecules   buckling   molecular dynamics simulation  

摘要： The functionalisation of carbon nanotubes (CNTs) with biomolecules in an aqueous environment has found considerable potential applications in nanobiotechnology. To understand the structural properties under physical adsorption and mechanical characteristics of non-covalently functionalised CNTs with four important biomolecules in aqueous environment, i.e. l-alanine, guanine, thymine and uracil, molecular dynamics (MD) simulations are performed. It is demonstrated that, unlike l-alanine, the main factor of adsorption is pi-pi stacking together with van der Waals (vdW) interactions. Computation of gyration radius reveals that gyration radius increases linearly as the weight percentage of functional biomolecules increases. Also, it is shown that the presence of water molecules leads to more expansion of biomolecules around CNTs. Simulations show that Young's modulus of the adsorbed CNTs is slightly smaller than that of pure ones. Furthermore, it is demonstrated that the critical buckling force of functionalised CNT is higher than that of pure CNT. Also, for high aspect ratios, the critical strain of functionalised CNTs is found to be lower than that of pure ones and changes linearly by increasing the weight percentage of functional biomolecules. The buckling modes of functionalised CNTs in vacuum and aqueous environments are explored.

关键词： CNT   polymer   polyoxymethylene   molecular dynamics   composite  

摘要： Carbon Nanotubes (CNTs) are potential additives to polymeric materials as they can enhance the mechanical, structural, and electronic properties of the resulting polymeric composite. However, the improvement of different properties is not always guaranteed and the results usually depend on the specific polymer used, along with the quality and quantity of CNTs used in the polymer composite. In this work, a reactive force field (ReaxFF) is applied to perform molecular dynamics (MD) simulation to determine the change in mechanical properties of single-walled carbon nanotube (SWCNT)-reinforced Polyoxymethylene (POM) composite. We have varied the diameter of CNTs from 0.542 to 1.08 nm keeping the temperature constant at room temperature (300 K) and observed a significant change in the resulting mechanical property. Volume fraction of CNT and temperature are also varied and the results are presented through a stress-strain plot. After that, our Molecular Dynamics (MD) simulation result of CNT is compared with existing literature for code validation. Dependence of mechanical property on the interaction energy, fracture mechanism, and reasons behind it are discussed elaborately. It is clear from the results that the use of SWCNT in the polymer matrix of POM significantly improves the mechanical property of SWCNT-reinforced POM composite.

关键词： combustion performance   dynamics   fiber   MHSH   PBS  

摘要： Environmental problems caused by polymers and polymers have historically dominated both academic and industrial attention. Sustainable biodegradable wood-plastic composites (WPCs) as an optimum can solve the environmentally critical problems caused by petroleum-based polymers. However, they are flammable, prone to fire accidents, and often have a contradiction between mechanical performance and flame-retardant properties, which limits their range of applications. Here, we reported a flame-retarded poly(butylene succinate) (PBS) WPC prepared with modified natural fiber-magnesium hydroxide sulfate whisker (MHSH) hybrids and intumescent flame retardants (IFRs). The mechanical performance, flame-retardant properties, thermal stability, and actual fire simulation parameters of composites were investigated. Owing to the unique composition characteristics of modified cassava dregs-MHSH hybrids, the mechanical properties (70P/23I/5C/2M, flexural strength was 39.2 +/- 1.960/MPa, impact strength was 7.95 +/- 0.3975/ [KJ/m(2)]), flame retardant properties (70P/23I/5C/2M, the limiting oxygen index value was 39.6%, UL-94 was V0) and thermal stability of WPC have been improved. Thereby, the balance between mechanical performance and flame retardant properties of biocomposites has been achieved in the practical engineering requirements. Furthermore, cone calorimeter data indicated that modified cassava dregs-MHSH hybrids played a role in improving the fire safety of composites. The total heat release, total smoke produce, toxic gas release, and total oxygen consumed of 70P/23I/5C/2M were lowered compared with those of 70P/25I/5C. Dynamics analysis indicated that the addition of modified cassava dregs-MHSH hybrids increased the activation energy of composites. Based on the experimental and analyses data, especially the morphological characterization of char residue analysis, it illustrated that modified cassava dregs-MHSH hybrids have a reinforcement and flame-retardant effect. The

关键词： graphene mechanical resonator   phonon-based information processing   coherent oscillation  

摘要： Vibrational modes in mechanical resonators provide a promising candidate to interface and manipulate classical and quantum information. The observation of coherent dynamics between distant mechanical resonators can be a key step toward scalable phonon-based applications. Here we report tunable coherent phonon dynamics with an architecture comprising three graphene mechanical resonators coupled in series, where all resonators can be manipulated by electrical signals on control gates. We demonstrate coherent Rabi oscillations between spatially separated resonators indirectly coupled via an intermediate resonator serving as a phonon cavity. The Rabi frequency fits well with the microwave burst power on the control gate. We also observe Ramsey interference, where the oscillation frequency corresponds to the indirect coupling strength between these resonators. Such coherent processes indicate that information encoded in vibrational modes can be transferred and stored between spatially separated resonators, which can open the venue of on-demand phonon-based information processing.

关键词： Poly(urethane-urea)   Amphiphilic   Self-assembly   Photoisomerization   Dynamic mechanical properties  

摘要： Azobenzene containing polymers have been used in the development of materials and devices responsive to light, devices for optical storage information, with shape-changing and shape-memory capacities, surface-relief grating, holograms, etc. Poly(urethane-urea)s (PUU) based on a hydrophilic polyethylene glycol (PEG-PUU), on a hydrophobic polycaprolactone diol (PCL-PUU) polyols, and on an equimolar mixture of them (PEG/PCL-PUU), 4,4'-diphenylmethane diisocyanate and 4,4'-diaminoazobenzene (DAAB), as a chain extender, were synthesized by a two-step route. PUU were characterized with respect to their chemical structure, molar masses, thermal and dynamic mechanical properties, and spectroscopic properties. The kinetics of the photo- and thermal-induced isomerization were studied in DMF solutions. The isomerization rate constant was two orders of magnitude higher for DAAB compared with PUU in DMF solution, except for PEG/PCL-PUU, for which the rate constant was half the value observed for DAAB. The amphiphilic nature of the PUU resulted in aggregates in DMF and, therefore, the azo isomerization for PEG-PUU and PCL-PUU occurred in a solid-state-like environment. On the other hand, PEG/PCL-PUU presented unimers and aggregates in DMF and the isomerization of azo groups in free PUU chains was faster. The PUU were semicrystalline and thermo-mechanically stable up 150 degrees C due to the hydrogen bonding involving urea, urethane and ester groups. The aggregates size in DMF solution, as well as the dynamic mechanical properties of the PUU, were sensitive to photo- and thermo-induced isomerization.

关键词： Dynamic membrane   Membrane fouling   Natural organic matter   Molecular dynamics simulations   Low-pressure filtration  

摘要： Membrane fouling caused by natural organic matter (NOM) in water is a pressing problem. To address this, heated aluminum oxide particles (HAOPs) have been used as dynamic membranes pre-deposited onto the primary membrane to effectively remove NOM and thereby significantly diminish the fouling potential. An in-depth understanding of the mechanisms underlying the superior performance of HAOPs remains amiss, which motivated this study. Molecular dynamics (MD) simulations were conducted to systematically compare the performance of HAOPs, which have been reported to be particularly effective for high molecular weight (HMW) NOM, with the conventional powdered activated carbon (PAC) adsorbent. Six NOM constituents, three of which have HMW and three have low molecular weight (LMW), were studied. Results indicate that the mechanisms underlying the effective removal of HMW NOM by HAOPs include: (1) higher foulant-HAOPs interaction energy;(2) greater hydration of the HMW NOM, which thereby increases the affinity to the more hydrophilic HAOPs;(3) diminished mobility of the foulant once adsorbed, which deters desorption;and (4) higher peak intensities in the radial distribution functions for multiple functional groups on the HMW NOM foulants. These results are expected to be valuable towards the better design of such materials for mitigating membrane fouling.

关键词： Chemical structure   Nanocomposites   Clay   Materials   Polymers  

摘要： Nacre-mimetic nanocomposites based on high fractions of synthetic high-aspect-ratio nanoclays in combination with polymers are continuously pushing boundaries for advanced material properties, such as high barrier against oxygen, extraordinary mechanical behavior, fire shielding, and glass-like transparency. Additionally, they provide interesting model systems to study polymers under nanoconfinement due to the well-defined layered nanocomposite arrangement. Although the general behavior in terms of forming such layered nanocomposite materials using evaporative self-assembly and controlling the nanoclay gallery spacing by the nanoclay/polymer ratio is understood, some combinations of polymer matrices and nanoclay reinforcement do not comply with the established models. Here, we demonstrate a thorough characterization and analysis of such an unusual polymer/nanoclay pair that falls outside of the general behavior. Poly(ethylene oxide) (PEO) and sodium fluorohectorite form nacre-mimetic, lamellar nanocomposites that are completely transparent and show high mechanical stiffness and high gas barrier, but there is only limited expansion of the nanoclay gallery spacing when adding increasing amounts of polymer. This behavior is maintained for molecular weights of PEO varied over four orders of magnitude and can be traced back to depletion forces. By careful investigation via X-ray diffraction and proton low-resolution solid-state NMR, we are able to quantify the amount of mobile and immobilized polymer species in between the nanoclay galleries and around proposed tactoid stacks embedded in a PEO matrix. We further elucidate the unusual confined polymer dynamics, indicating a relevant role of specific surface interactions.