Study of protein adsorption on octacalcium phosphate surfaces by molecular dynamics simulations

This study numerically studies absorption of human serum albumin (HSA) and basic protein lysozyme (LSZ) on crystallographic planes of octacalcium phosphate (OCP), an essential bioactive calcium phosphate. The molecular simulations include constructing atomic structure of OCP crystallographic planes and representative segments of HSA and LSZ with three different initiate orientations respect to OCP planes. The simulation reveals the dynamic process of the protein absorption. The absorption behavior of proteins is quantified by the interaction energy between proteins and OCP planes and the strain energy of proteins in absorption. The results show that absorption interaction energy of basic LSZ is higher than that of acidic HSA, which indicates that LSZ is more favorable to adsorb onto OCP surface than HSA. The interaction energies change with the OCP crystallographic planes, the trend of changes for both proteins are similar, that is OCP (001) > OCP (111) > OCP (110) > OCP (100), which is corrected with surface energy variation of crystallographic planes. The strain energy strongly depends on the orientations of the proteins before absorption, but weakly depends on crystallographic planes. The simulation results provide useful significant information for predicting/designing interface between bioceramic materials and organic tissues as well as for understanding the mechanism of the osteoinductivity at an atomic level.     

Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocrystals on single-walled carbon nanotubes as a highly efficient oxygen-evolving catalyst

The efficient catalytic oxidation of water to dioxygen is envisioned to play an important role in solar fuel production and artificial photosynthetic systems. Despite tremendous efforts, the development of oxygen evolution reaction (OER) catalysts with high activity and low cost under mild conditions remains a great challenge. In this work, we develop a hybrid consisting of Co₃O₄ nanocrystals supported on single-walled carbon nanotubes (SWNTs) via a simple self-assembly approach. A Co₃O₄/SWNTs hybrid electrode for the OER exhibits much enhanced catalytic activity as well as superior stability under neutral and alkaline conditions compared with bare Co₃O₄, which only performs well in alkaline solution. Moreover, the turnover frequency for the OER exhibited by Co₃O₄/SWNTs in neutral water is higher than for bare Co₃O₄ catalysts. Synergetic chemical coupling effects between Co₃O₄ nanocrystals and SWNTs, revealed by the synchrotron X-ray absorption near edge structure (XANES) technique, can be regarded as contributing to the activity, cycling stability and stable operation under neutral conditions. Use of the SWNTs as an immobilization matrix substantially increases the active electrode surface area, enhances the durability of catalysts under neutral conditions and improves the electronic coupling between Co redox-active sites of Co₃O₄ and the electrode surface.      

Multiscale modeling of nano/micro systems by a multiscale continuum field theory

This paper presents a multiscale continuum field theory and its application in modeling and simulation of nano/micro systems. The theoretical construction of the continuum field theory will be briefly introduced. In the simulation model, a single crystal can be discretized into finite element mesh as in a continuous medium. However, each node is a representative unit cell, which contains a specified number of discrete and distinctive atoms. Governing differential equations for each atom in all nodes are obtained. Material behaviors of a given system subject to the combination of mechanical loadings and temperature field can be obtained through numerical simulations. In this work, the nanoscale size effect in single crystal bcc iron is studied, the phenomenon of wave propagation is simulated and wave speed is obtained. Also, dynamic crack propagation in a multiscale model is simulated to demonstrate the advantage and applicability of this multiscale continuum field theory.     

An investigation of Interface-GMRES(R) for fluid–structure interaction problems with flutter and divergence

The basic subiteration method for solving fluid–structure interaction problems consists of an iterative process in which the fluid and structure subsystems are alternatingly solved, subject to complementary partitions of the interface conditions. The main advantages of the subiteration method are its conceptual simplicity and its modularity. The method has several deficiencies, however, including a lack of robustness and efficiency. To bypass these deficiencies while retaining the main advantages of the method, we recently proposed the Interface-GMRES(R) solution method, which is based on the combination of subiteration with a Newton–Krylov approach, in which the Krylov space is restricted to the interface degrees-of-freedom. In the present work, we investigate the properties of the Interface-GMRES(R) method for two distinct fluid–structure interaction problems with parameter-dependent stability behaviour, viz., the beam problem and the string problem. The results demonstrate the efficiency and robustness of the Interface-GMRES(R) method.     

A homogenous CS/NaCMC/n-HA polyelectrolyte complex membrane prepared by gradual electrostatic assembling

A homogenous membrane composed of chitosan (CS), sodium carboxymethyl cellulose (NaCMC) and nano hydroxyapatite (n-HA) was prepared by a gradual electrostatic assembling (GEA) method. The physical and chemical properties of the membranes with different n-HA contents and CS/NaCMC ratios were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and mechanical test. The schematic formation mechanism of the membrane was discussed. The results show that GEA is an effective method to prepare the polyelectrolyte complex (PEC) membrane, in which oppositely charged CS-NaCMC polysaccharides can assemble mildly and gradually through electrostatic interaction to form the membrane framework, while the filled n-HA crystals can regulate the structure stability of the composite membrane. The optimum preparation condition for the PEC membrane can be fixed to a content of 60 wt% n-HA, an equivalent amount of CS to NaCMC and a drying temperature of 60°C. The PEC membrane may have good prospect for guided bone regeneration.     

Coexistence of Superconductivity and Ferromagnetism

An overview of the problem of the coexistence of superconductivity and ferromagnetism in uranium-based superconductors such as UGe₂, URhGe, UCoGe, UIr and ZrZn₂ will be briefly presented. Starting with a pairing Hamiltonian with equal spin superconducting triplet pairs and using quantum field theory Green function formalism, the coexistent ferromagnetic order with superconductivity will be shown to be a very distinct possibility. The singlet superconductivity coexisting with ferromagnetism is against the experimental observations. It will be argued that the superconductivity can be destroyed at two points as a result of magnetic fields both intrinsic and or extrinsic, and thus establishing reentrant superconductivity as observed most recently in URhGe. In the absence of consensus on the mechanism, the same is not highlighted although the magnetic quantum fluctuations emanating from quantum critical point could provide the pairing. The limitations of the model will also be discussed.     

An extended graphical targeting technique for direct reuse/recycle in concentration and property-based resource conservation networks

Minimum flowrate targeting methods for resource conservation networks (RCNs) have been developed over the last decades. The existing methodologies still have certain drawbacks. Their design insights could be deepened and some steps should be more convenient for the users. A targeting tool called the material surplus composite curve (MSCC), which is an improvement of the surplus diagram for water and hydrogen networks is introduced. The approach is illustrated on several cases selected from the literature. Using this technique, it is possible to determine rigorous flowrate targets for different variants of the RCN problem.     

Nanoalumina-supported Mn2O3 as efficient adsorbent for removal of fluoride and arsenic from water: a study from lab to field

Journal of Materials Science - Water pollution with heavy metals has been a problem for the environment and human health. The cohabitation of As(III) and fluoride in groundwater has gotten...     

Green and gold kiwifruit peel ethanol extracts potentiate pentobarbital-induced sleep in mice via a GABAergic mechanism

Kiwifruit is one of the most popular fruits worldwide, and it has various biological properties, including antioxidant, anti-allergic, and cardiovascular protective effects. The peel of kiwifruit, which is a by-product of processing, is a good source of flavonoids; however, its bioactivity has not been widely investigated. In this study, we evaluated the hypnotic effects of green (GRPE, Actinidia deliciosa) and gold (GOPE, Actinidia chinensis) kiwifruit peel ethanol extracts and their solvent fractions, and the possible underlying mechanisms. Oral GRPE and GOPE administration (125–1000 mg/kg) produced a dose-dependent decrease in sleep latency and an increase in sleep duration in pentobarbital-treated mice. Among three different solvent fractions of GRPE and GOPE, ethyl acetate (EA) fractions had the greatest effect on sleep duration at 250 mg/kg. The total flavonoid contents of solvent fractions were proportional to sleep duration. Like diazepam (a GABA_A–benzodiazepine (BZD) receptor agonist), the hypnotic effects of GRPE, GOPE, and their EA fractions were fully inhibited by flumazenil (a GABA_A–BZD receptor antagonist). These results suggest that potentiation effects of GRPE and GOPE on pentobarbital-induced sleep in mice may be modulated by a GABAergic mechanism.     

Unfreezable Water in Apple Treated by Pulsed Electric Fields: Impact of Osmotic Impregnation in Glycerol Solutions

The effects of pulsed electric fields (PEF) and osmotic impregnation in glycerol solution on the amount of unfreezable water in apple were determined by means of low-temperature differential scanning calorimetry (DSC). The obtained data were compared with behaviour of pure water–glycerol solutions (sample WG). PEF treatment was applied using a near-rectangular monopolar generator with pulse duration of 100 μs at electric field strength of 800 V/cm. The osmotic impregnation of PEF-treated apple discs was done using water–glycerol (sample AWG) and apple juice–glycerol (sample AJG) osmotic solutions at different concentration of water or juice in glycerol, W = 30–100 wt%. The data evidenced that for the PEF-treated samples the glycerol was able to penetrate successfully inside apple tissue. The state diagrams for WG, AWG and AJG samples were rather similar. It was observed that free water existed only for moisture content above some minimum value. The unfreezable water content was the largest in AJG, followed by WG and AWG. The juice concentration in glycerol W ≈ 80 wt% was found to be optimal for preservation of the texture of PEF-treated samples.