ABSTRACT
A nanocomposite consisting of gold nanoparticles (AuNP), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) was synthesized using a co-reduction strategy in ethylene glycol using sodium citrate as the reducing agent. The nanocomposite was successfully characterized using X-ray powder diffraction, scanning electron microscopy and electrochemical methods. The material was deposited on a glassy carbon electrode and then was found to have high electrocatalytic capability for the electrode process of nitrite. This is attributed to the synergic actions of rGO, MWCNTs and AuNPs. Based on this, an amperometric nitrite sensing scheme was worked out that had attractive features: (a) a wide linear range that extends from 50 nM to 2.2 mM, (b) a working potential of 0.80 V (vs.SCE) at pH 5.0, (c) a 14 nM detection limit (at an SNR of 3), and (d) an electrochemical sensitivity of 1201 µA·mM-1·cm-2. The sensor was successfully applied to the determination of nitrite in the local river water. Graphical abstract Schematic presentation of the fabrication of the AuNPs-rGO-MWCNTs composite modified electrode and its application for the nitrite electrochemical sensing.
ABSTRACT
BACKGROUND: Existing flaws have been found in the production process of poly(lactic-co-glycolic acid) (PLGA) copolymer microspheres, which lead to residual solvent, low drug loading rate and low encapsulation efficiency of sustained-release microspheres.OBJECTIVE: To review different methods for preparing PLGA microspheres from the following aspects: basic principles, advantages/disadvantages, indications and future development. METHODS: We retrieved CNKI, PubMed and Google scholar to access the articles related to the technique process of preparing PLGA microspheres published from January 2012 to April 2017, including experiment and application research on the principles and advantages/disadvantages of the various processes. RESULTS AND CONCLUSION: To date, the main methods to prepare PLGA microspheres include single/re-emulsion solvent evaporation method, spray drying method, hydrogel template method, microfluid, coaxial electrostatic spraying, phase separation method, and supercritical fluid extraction. However, no valid evidences suggest that there is a technique that completely solves all potential problems, such as drug encapsulation and release, residual solvent and appropriate shape and size. Combination and modification of the production processes is expected to develop novel PLGA microspheres with ideal encapsulation efficiency and stable drug release.
ABSTRACT
With the classical ensemble method, the correlated-electron dynamics of Mg atom from a doubly excited, transition Coulomb complex in few-cycle circularly polarized (CP) laser field at low laser intensity is theoretically investigated. The low energy transfer during the recollision process indicates that the two electrons cannot release directly, but it can pass through a doubly excited state, and then escape with the ionization time difference. The numerical results show that the feature of the sequential double ionization (SDI) can be observed in the nonsequential double ionization (NSDI) process. The SDI-like results demonstrate that the intermediate state has lost any memory of its formation dynamics. The distribution of the angle between the two release directions of the two electrons also depends on the ionization time difference. Finally, the influence of e-e Coulomb repulsion is discussed.
ABSTRACT
<p><b>OBJECTIVES</b>To investigate the mechanical properties of bilateral atlantoaxial trans-articular screws and atlas laminar hooks instrumentation with finite element method.</p><p><b>METHODS</b>There was a volunteer with age of 28 years old, body height 172 cm, body weight of 60 kg and without cervical deformity by X rays. The ligamentous, nonlinear, three-dimensional finite element models of normal upper cervical spine (C0-3) was developed and validated. The destabilized model with bilateral atlantoaxial trans-articular screws and atlas laminar hooks was evaluated for quasistatic loading.</p><p><b>RESULTS</b>The finite element model of upper cervical spine consists of 229,047 nodes and 152,475 elements, and correlated well with experimental data for all load cases and could be used for experiment. The finite model with bilateral atlantoaxial trans-articular screws and atlas-laminar hooks predicted that the maximum Von Mises Stress was in the region in which screws penetrated the atlantoaxial articular facet. The novel instrumentation resulted in sufficient stability.</p><p><b>CONCLUSION</b>The bilateral atlantoaxial trans-articular screws and atlas laminar hooks instrumentation is useful and effective for atlantoaxial arthrodesis.</p>
