Traumatic injuries to the brain and spinal cord of the central nervous system (CNS) lead to severe and permanent neurological deficits and to date there is no universally accepted treatment. Owing to the profound impact, extensive studies have been carried out aiming at reducing inflammatory responses and overcoming the inhibitory environment in the CNS after injury so as to enhance regeneration. Artificial scaffolds may provide a suitable environment for axonal regeneration and functional recovery, and are of particular importance in cases in which the injury has resulted in a cavitary defect. In this review we discuss development of scaffolds for CNS tissue engineering, focusing on mechanism of CNS injuries, various biomaterials that have been used in studies, and current strategies for designing and fabricating scaffolds.
Carbon nanostructures, including carbon nanotubes (CNTs) and graphene, have been studied extensively due to their special structures, excellent electrical properties and high chemical stability. With the development of nanotechnology and nanoscience, various methods have been developed to synthesize CNTs/graphene and to assemble them into microelectronic/sensor devices. In this review, we mainly demonstrate the latest progress in synthesis of CNTs and graphene and their applications in field-effect transistors (FETs) for biological sensors.
The objective of the present study is to systematically evaluate the role of polymer crystallinity on fibroblast and osteoblast adhesion and proliferation using a series of poly(caprolactone-
Nanocapacitors and nonvolatile ferroelectric random access memories require nanoscale thin film coatings with ferroelectric properties. One dimensional ferroelectric nanofibers are used in ferroelectric memory devices owing to the fact that decrease of the dimensionality of the memory device elements will reduce the addressing and appreciably increase the storage capacity. Novel ZnO/BaO nanocomposite fibers exhibiting ferroelectric properties have been prepared in the form of non-woven mesh by electrospinning the sol derived from the sol-gel route. Thin cylindrical nanofibers of average diameter 100 nm have been obtained and their morphology is confirmed by SEM and AFM images. In the electrospinning process, the effect of the working distance on the fiber morphology was studied and it showed that working distance between 11 and 15 cm can produce fibers without beads and the decrease in working distance in this range increases the fiber diameter. Powder XRD was used to identify the phases and EDX analysis confirmed the presence of ZnO/BaO. Dielectric and non-linear optical properties have also been studied. The dielectric studies showed that ZnO/BaO composite nanofibers undergo a phase transition from ferroelectric to paraelectric at 323 K.
The effective thermal conductivity of heterogeneous or composite materials is an essential physical parameter of materials selection and design for specific functions in science and engineering. The effective thermal conductivity is heavily relied on the fraction and spatial distribution of each phase. In this work, image-based finite element method (FEM) was used to calculate the effective thermal conductivity of porous ceramics with different pore structures. Compared with former theoretical models such as effective media theory (EMT) equation and parallel model, image-based FEM can be applied to a large variety of material systems with a relatively steady deviation. The deviation of image-based FEM computation mainly comes from the difference between the two dimensional (2D) image and the three dimensional (3D) structure of the real system, and an experiment was carried out to confirm this assumption. Factors influencing 2D and 3D effective thermal conductivities were studied by FEM to illustrate the accuracy and application conditions of image-based FEM.
We adopt molecular dynamics (MD) method to extensively study the dynamical process during the crack propagation along two crystallographic directions in the two-dimensional close-packed system. The dependence of crack initiation time on the loading rates is investigated in comparison with continuum analysis. By calculating the displacement and stress field, the results are in excellent agreement with the asymptotic continuum solution of low-speed propagating crack. Moreover, the crack-tip velocity is numerically attained and associated with the instability of crack surface morphology, which results from the strongly anisotropic behavior. Further analysis remarkably observes the crack-branching healing process in that the dislocation emission absorbs the concentrated strain energy of crack tip.