In the present study we focused on the in vitro and in vivo evaluation of two types of carbon fibres (CFs): hydroxyapatite modified carbon fibres and porous carbon fibres. Porous CFs used as scaffold for tissues regeneration could simultaneously serve as a support for drug delivery or biologically active agents which would stimulate the tissue growth; while addition of nanohydroxyapatite to CFs precursor can modify their biological properties (such as bioactivity) without subsequent surface modifications, making the process cost and time effective. Presented results indicated that fibre modification with HAp promoted formation of apatite on the fibre surface during incubation in simulated body fluid. The materials biocompatibility was determined by culturing human osteoblast-like cells of the line MG 63 in contact with both types of CFs. Both tested materials gave good support to adhesion and growth of bone-derived cells. Materials were implanted into the skeletal rat muscle and a comparative analysis of tissue reaction to the presence of the two types of CFs was done. Activities of marker metabolic enzymes: cytochrome c oxidase (CCO) and acid phosphatase were examined to estimate the effect of implants on the metabolic state of surrounding tissues. Presented results evidence the biocompatibility of porous CFs and activity that stimulates the growth of connective tissues. In case of CFs modified with hydroxyapatite the time of inflammatory reaction was shorter than in case of traditional CFs.

No abstract

No abstract

Novel cellulose fibres (Biocelsol) were spun by traditional wet spinning technique from the alkaline solution prepared by dissolving enzyme treated pulp directly into aqueous sodium zincate (ZnO/NaOH). The spinning dope contained 6 wt.% of cellulose, 7.8 wt.% of sodium hydroxide (NaOH) and 0.84 wt.% of zinc oxide (ZnO). The fibres were spun into 5% and 15% sulphuric acid (H 2 SO 4 ) baths containing 10% sodium sulphate (Na 2 SO 4 ). The highest fibre tenacity obtained was 1.8 cNdtex -1 with elongation of 15% and titre of 1.4 dtex. Average molecular weights and shape of molecular weight distribution curves of the celluloses from the novel wet spun cellulosic fibre and from the commercial viscose fibre were close to each other.

No abstract

No abstract

We present a study of anisotropy of transport and magnetic properties in a La1−xCaxMnO3 (x ≈ 1/3) film prepared by pulsed-laser deposition onto a LaAlO3 substrate. We found a non-monotonic dependence of magnetoresistance (MR) on magnetic field H for both H perpendicular and parallel to the film plane but perpendicular to the current. In the longitudinal geometry (when H is parallel to both the current and the film plane) the MR was negative at all fields below 20 kOe, as expected for colossal-magnetoresistance manganites. This rather complex behavior of MR manifests itself at rather low temperatures, far below the Curie temperature Tc, which was close to room temperature. Two main sources of MR anisotropy in the film have been considered in the explanation of the results: (1) the existence of preferential directions of magnetization (due to strains stemming from the lattice film-substrate mismatch or other reasons); (2) dependence of resistance on the angle between current and the magnetization, which is inherent in ferromagnets. The transport and magnetic properties of the film correspond well to this view. In particular, the following angle dependence of MR is found: R(θ)/R(0) = 1 + δan(T, H) sin 2 θ (where θ is the angle between the field and current directions in the plane normal to the film but parallel to the current). The temperature and magnetic field dependences of δan(T, H) were recorded and analyzed. A clear magnetization anisotropy, that generally favors the magnetization in the film plane is also found. At the same time the recorded magnetization curves (as well as the MR data) indicate, that the film crystal structure should be inhomogeneous in such a way that various parts of the films have non-identical magnetic properties (with different directions of spontaneous magnetization). This hypothesis is supported by X-ray diffraction which revealed that the film is inhomogeneous in strain, lattice parameter and lattice orientation. This peculiar macroscopic-scale disorder is caused by a film-substrate interaction. The possible reasons for formation of such structure and its effect on MR anisotropy are considered.

No abstract