Ultrasensitive solution-phase electrochemical molecular beacon-based DNA detection with signal amplification by exonuclease III-assisted target recycling

Taking advantage of the preferential exodeoxyribonuclease activity of exonuclease III in combination with the difference in diffusivity between an oligonucleotide and a mononucleotide toward a negatively charged ITO electrode, a highly sensitive and selective electrochemical molecular beacon (eMB)-based DNA sensor has been developed. This sensor realizes electrochemical detection of DNA in a homogeneous solution, with sensing signals amplified by an exonuclease III-based target recycling strategy. A hairpin-shaped oligonucleotide containing the target DNA recognition sequence, with a methylene blue tag close to the 3' terminus, is designed as the signaling probe. Hybridization with the target DNA transforms the probe's exonuclease III-inactive protruding 3' terminus into an exonuclease III-active blunt end, triggering the digestion of the probe into mononucleotides including a methylene blue-labeled electro-active mononucleotide (eNT). The released eNT, due to its less negative charge and small size, diffuses easily to the negative ITO electrode, resulting in an increased electrochemical signal. Meanwhile, the intact target DNA returns freely to the solution and hybridizes with other probes, releasing multiple eNTs and thereby further amplifies the electrochemical signal. This new immobilization-free, signal-amplified electrochemical DNA detection strategy shows great potential to be integrated in portable and cost-effective DNA sensing devices.     

Singularity analysis of three-legged, six-DOF platform manipulators with URS legs

A special class of platform manipulators is the subject of this paper. These manipulators comprise two platforms connected by three legs, each being composed of one universal (U), one revolute (R) and one spherical (S) joints, which gives the manipulator six degrees of freedom. Hence, two actuators are required per leg. Under the assumption that the two R joints proximal to the fixed platform, and making up the U-joint, are actuated, we derive the differential kinematic relations between actuator joint rates and mobile-platform twist. This model comprises two Jacobian matrices, the forward- and inverse-kinematics Jacobians. These relations are then applied to the singularity analysis of the parallel manipulator developed at Singapore Institute of Manufacturing Technology and Nanyang Technological University.     

Flexible graphite-based integrated anode plate for direct methanol fuel cells at high methanol feed concentration

An integrated anode plate suitable for operating direct methanol fuel cells (DMFCs) at a high methanol feed concentration is reported. This anode structure which was made of flexible graphite materials not only provides dual role of liquid diffusion layer and flow field plate, but also serves as a methanol blocker by decreasing methanol flux to the interface of catalyst and membrane electrolyte. DMFCs incorporating this new anode structure exhibited a much higher open circuit voltage (OCV) (∼0.51 V) than that (∼0.42 V) of a conventional DMFC at a 10 M methanol feed. Cell polarization data show that this new anode structure significantly improves the cell performance at high methanol concentration scenarios (e.g. 12 M or above). Moreover, this new design greatly simplifies the anode structure and offers a promising approach in running passive-mode DMFC at high methanol feed concentrations.     

Compare the effects of chondrogenesis by culture of human mesenchymal stem cells with various type of the chondroitin sulfate C

Chondroitin sulfate C (CSC) is a kind of glycosaminoglycans (GAGs) with molecular weights of 10,000 to 50,000 Da and a high charge density. GAGs are major components in extracellular matrix (ECM), which play important role in the regulation of cell proliferation, migration, and differentiation. In this study, we studied the effects of chondroitin sulfate C (CSC) on the differentiation of human mesenchymal stem cells (MSCs) toward the chondrocyte lineage. The MSCs were either cultured on type II collagen (COL II) scaffolds with high molecular weight CSC addition in the medium (free CSC) or with free oligosaccharide CSC. Special attention was given to the effects of MSCs cultured on CSC cross-linked type II scaffolds (cross-linked CSC). According to the analysis of histology stain, gene expression, and ECM secretion, our results showed that MSCs cultured with free CSC, free oligosaccharides CSC, and on the cross-linked CSC scaffolds all would be induced into chondrocytes. Moreover, free oligosaccharide CSC present in the microenvironment could significantly up-regulate MSC chondrogenesis gene expression and stimulate cartilage ECM accumulation more than free CSC with high molecular weight after 3-week induction. Importantly, cross-linked CSC had the most excellent effects on the MSC chondrogenesis. Thus, we believed that cross-linked CSC in the scaffold would play the similar roles with free oligosaccharide CSC in the medium. Cross-linked CSC would be a potential candidate for cartilage repair in the cell therapy and tissue engineering.     

Synthesis of bimetallic PdAu nanoparticles for formic acid oxidation

In this work, a simple co-deposition strategy for the synthesis of carbon-supported Pd–Au alloy was reported. Our approach involves the co-reduction of Au and Pd ions using ethylene glycol and sodium citrate as the reducing and stabilizing reagents. Both alloy and non-alloy bimetallic Pd–Au nanoparticles are produced using a right rate-limiting strategy. For example, when ethylene glycol and sodium citrate are the limiting reagent with Au and Pd ions in excess, the synthesis environment favors preferential nucleation and growth of Au nanoparticles followed by deposition of Pd either as the shell of Au core or as separate Pd clusters. On the other hand, if the supply of metal ions (not the reducing reagents) limits the reaction, it creates a synthesis condition for Pd–Au alloy particles. The as-prepared Pd–Au alloys exhibit higher Pd-specific activities towards formic acid oxidation compared with the non-alloy counterpart or individual Pd catalyst and an easier removal of adsorbed oxygen species (e.g., O_ads or OH_ads) was observed from the surface of Pd–Au alloy with a higher content of Au.     

The effects of doped Nd on conductivity and phase stability of BaCe0.8Y0.2O3−δ-based electrolyte for solid oxide fuel cell

This study investigates the structure, phase stability, and electrical properties of BaCe_0.8Y_0.2−xNd_xO_3−δ (x = 0-0.2) in humid air. XRD results indicate that a BaCe_0.8Y_0.2−xNd_xO_3−δ sample has an asymmetric orthorhombic structure, and this structure becomes more symmetric as the amount of Nd doping increases. The conductivity of BaCe_0.8Y_0.2−xNd_xO_3−δ depends on the amount of Nd doping and the operation temperature. AC impedance results indicate that the resistance of BaCe_0.8Y_0.2−xNd_xO_3−δ decreases as the temperature increases, with the majority of resistance coming from oxygen ion diffusion. The XRD peak intensity of BaCe_0.8Y_0.2O_3−δ apparently decreased with time, forming Ba(OH)₂ and CeO₂ second phases. The phase stability of BaCe_0.8Y_0.2−xNd_xO_3−δ (x = 0.05-0.2) samples is much better than that of BaCe_0.8Y_0.2O_3−δ, and it exhibited no second phase after tested in an 80 °C water bath for 18 h.     

Anisotropic Supercurrent in Strained Graphene Josephson Junction

The Weyl?CDirac fermions in graphene-based SG/I/SG (SG denoting superconducting graphene; I, an insulator) junctions subjected to strains become highly asymmetric. The effect of the strain-induced symmetry change of the fermions on the supercurrent is studied. The highly anisotropic velocity near the critical deformation causes the critical current parallel to the direction of strain to oscillate as a function of gate voltage at a very high frequency. The same anisotropic velocity destroys the oscillation of the gate-dependent critical current when the current is perpendicular to the direction of strain. The direction-dependent supercurrent is due to the strain turning the two-dimensional massless relativistic electrons into nearly one-dimensional massless relativistic fermions near the critical deformation. This work reveals that a new effect can be induced by applying strain on a graphene-based Josephson junction.     

A virtual reality system for arm and hand rehabilitation

This paper presents a virtual reality (VR) system for upper limb rehabilitation. The system incorporates two motion track components, the Arm Suit and the Smart Glove which are composed of a range of the optical linear encoders (OLE) and the inertial measurement units (IMU), and two interactive practice applications designed for driving users to perform the required functional and non-functional motor recovery tasks. We describe the technique details about the two motion track components and the rational to design two practice applications. The experiment results show that, compared with the marker-based tracking system, the Arm Suit can accurately track the elbow and wrist positions. The repeatability of the Smart Glove on measuring the five fingers’ movement can be satisfied. Given the low cost, high accuracy and easy installation, the system thus promises to be a valuable complement to conventional therapeutic programs offered in rehabilitation clinics and at home.     

Integrated design of legged mechatronic system

This paper presents a system based on the integrated design and experiment for a one degree-of-freedom (DOF) legged mechatronic system (LMTS). A six-bar linkage mechanism, which is derived from a four-bar linkage with a symmetrical coupler point and pantograph into one, is designed, and common controllers are used to control the velocity and position loops. For system-based dynamic optimization, the design for control (DFC) approach is used to integrate the structure and control for improving dynamic performance with reduced control torque. Finally, for a rapid 3D graphical based implementation of the system, high-level computer-aided rapid system integration (CARSI) technology is used to integrate the structure design, controller design, and system implementation into the design and analytical software environment based on Pro/engineer, XML syntax, Simmechanics, and Simulink. Thus, the development time for the LMTS is reduced.