Enhancement of the performance of covalently immobilized lipase using alcohol quenching technology

In order to modulate the microenvironment for enzyme covalently attached on support and improve the covalent immobilization of lipase, alcohol molecules were used to quench the excessive activated functional group on support surface. Effects of kind and content of alcohol molecules on the relative activity of the immobilized enzyme and the characteristics of the immobilized enzyme were examined carefully. The maximum relative activities of the immobilized lipase quenched with methanol and npropanol, were 224.3 and 224.5%, respectively, both 1.96 fold of the just immobilized lipase which was not quenched with alcohol. Residual activity of the immobilized lipase using methanol to quench the excessive activated groups on support surface was 65.9% after heating at 50°C for 60 h, 1.29 folds higher than that of the ordinarily immobilized lipase (with no blockage). Alcohol molecules could alter the physical and chemical properties to modulate the microenvironment on support surface bychanging the hydrophobicity. Suitable microenvironment, resulted from the methanol quenching the excessive active groups, would further favor the activity and the stability of lipase at higher temperature

Model testing on rainfall-induced landslide of loose soil in Wenchuan earthquake region

This study investigates the formation process of rainfall-induced landslide for slopes composed of loose soil in the Wenchuan earthquake region. Experimental investigations have been performed on the landslide's formation and the variation of the controlling soil parameters under various artificial rainfall conditions. The landslide triggering mechanisms can be described in the following way. Firstly, the large porosity of the loose soil facilitated the infiltration of water, which increased the pore water pressure and reduced the shear strength of the soil significantly. In addition, the rainfalls probably caused the concentration of finer particles at a certain depth of the valley slopes. This concentration within the soil increased the pore water pressure significantly, and consequently reduced both the porosity ratio and permeability. Therefore, when the pore water pressure reached a critical state, the effective shear strength of the soil diminished, inducing the landslide's formation

EVOLVING CONCEPTS OF CHONDROGENIC DIFFERENTIATION: HISTORY, STATE-OF-THE-ART AND FUTURE PERSPECTIVES

As a cell source, multipotent mesenchymal stromal cells or mesenchymal stem cells (MSCs) are promising candidates for chondrogenic differentiation and subsequent cartilage regeneration. From previous literature, it is known that chondrogenic differentiation of MSCs inevitably leads to hypertrophy and subsequent endochondral ossification. In this review, we examine the history of currently established protocols of chondrogenic differentiation and elaborate on the roles of individual components of chondrogenic differentiation medium. We also summarise the effects of physical, chemical and biological factors involved, and propose potential strategies to differentiate MSCs into articular chondrocytes with homogenous mature phenotypes through spatial-temporal incorporation of cell differentiation and chondrogenesis

Promising thermoelectric performance in van der Waals layered SnSe2

SnSe as a lead-free IV–VI semiconductor, has attracted intensive attention for its potential thermoelectric applications, since it is less toxic and much cheaper than conventional PbTe and PbSe thermoelectrics. Here we focus on its sister layered compound SnSe2 in n-type showing a thermoelectric performance to be similarly promising as SnSe in the polycrystalline form. This is enabled by its favorable electronic structure according to first principle calculations, its capability to be effectively doped by bromine on selenium site to optimize the carrier concentration, as well as its intrinsic lattice thermal conductivity as low as 0.4 W/m-K due to the weak van der Waals force between layers. The broad carrier concentration ranging from 0.5 to 6 × 1019 cm−3 realized in this work, further leads to a fundamental understanding on the material parameters determining the thermoelectric transport properties, based on a single parabolic band (SPB) model with acoustic scattering. The layered crystal structure leads to a texture in hot-pressed polycrystalline materials and therefore anisotropic transport properties, which can be well understood by the SPB model. This work not only demonstrates SnSe2 as a promising thermoelectric material but also guides the further improvements particularly by band engineering and texturing approaches

Low-Symmetry Rhombohedral GeTe Thermoelectrics

High-symmetry thermoelectric materials usually have the advantage of very high band degeneracy, while low-symmetry thermoelectrics have the advantage of very low lattice thermal conductivity. If the symmetry breaking of band degeneracy is small, both effects may be realized simultaneously. Here we demonstrate this principle in rhombohedral GeTe alloys, having a slightly reduced symmetry from its cubic structure, to realize a record figure of merit (zT ∼ 2.4) at 600 K. This is enabled by the control of rhombohedral distortion in crystal structure for engineering the split low-symmetry bands to be converged and the resultant compositional complexity for simultaneously reducing the lattice thermal conductivity. Device ZT as high as 1.3 in the rhombohedral phase and 1.5 over the entire working temperature range of GeTe alloys make this material the most efficient thermoelectric to date. This work paves the way for exploring low-symmetry materials as efficient thermoelectrics. Thermoelectric materials enable a heat flow to be directly converted to a flow of charge carriers for generating electricity. The crystal structure symmetry is one of the most fundamental parameters determining the properties of a crystalline material including thermoelectrics. The common belief currently held is that high-symmetry materials are usually good for thermoelectrics, leading to great efforts having historically been focused on GeTe alloys in a high-symmetry cubic structure. Here we show a slight reduction of crystal structure symmetry of GeTe alloys from cubic to rhombohedral, enabling a rearrangement in electronic bands for more transporting channels of charge carriers and many imperfections for more blocking centers of heat-energy carriers (phonons). This leads to the discovery of rhombohedral GeTe alloys as the most efficient thermoelectric materials to date, opening new possibilities for low-symmetry thermoelectric materials. Cubic GeTe thermoelectrics have been historically focused on, while this work utilizes a slight symmetry-breaking strategy to converge the split valence bands, to reduce the lattice thermal conductivity and therefore realize a record thermoelectric performance, all enabled in GeTe in a rhombohedral structure. This not only promotes GeTe alloys as excellent materials for thermoelectric power generation below 800 K, but also expands low-symmetry materials as efficient thermoelectrics

Development of a flexible endoscopic robot with autonomous tracking control ability using machine vision and deep learning

A flexible endoscopic robot is designed to solve the problem that it is difficult for auxiliary doctors to maintain a stable visual field in traditional endoscopic surgery. Based on geometric derivation, a motion control method under the constraint of the remote center motion (RCM) of the robot system is established, and a set of circular trajectories are planned for it. The RCM error of the robot during operation and the actual trajectory of the robot end in three-dimensional space are obtained through the motion capture system. The end of the robot is controlled by the heterogeneous primary–secondary teleoperation control algorithm based on position increments. Finally, the RTMDet deep learning object detection algorithm was selected to identify and locate surgical instruments through comparative experiments, and the autonomous tracking control was completed based on visual guidance. In the process of autonomous tracking, the RCM error was less than 1 mm, which met the actual surgical requirements.</p