Hollow core's inner surface coating in a photonic bandgap fibre (PBGF) is investigated by means of finite element method. The coat material and thickness-dependence dispersion curve and group velocity dispersion are numerically studied. The coating with materials of low index or small thickness will rise up the dispersion curve but will not induce surface modes. However, coating with materials of high index or big coat thickness will induce surface modes and avoided-crossings. By varying coat material's refractive index and thickness, the appearances of surface modes and avoided-crossings can be changed. It is found that the avoided-crossing can enormously enlarge the negative dispersion which can find applications in dispersion compensation. We numerically achieve a negative dispersion as large as −21416.15 ps/nm/km. The results give a physical insight into the propagation properties of PBGFs with the hollow core coated by a layer of material and are of crucial significance in the applications of PBGF coating.

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A new ready-to-use medicinal form -granules containing isoniazid and pyridoxine hydrochloride (0.15 and 0.015 g per gram of granules, respectively) -has been recently developed. An HPLC technique for the qualitative and quantitative analysis of the new preparation is described. The analyses are carried out using a Millihrom-2 chromatograph equipped with a UV detector and a KAKh 4-64-3 column filled with Separon C 18 . The column is eluted with an acetonitrile -0.5% aqueous sodium dihydrophosphate solution (60:40, adjusted with orthophosphoric acid at pH 2.5 -3.0) at a flow rate of 50 ml/min. The detection is carried out at 280 nm. The relative error of determination does not exceed ± 1.1% for isoniazid and ± 4.1% for pyridoxine hydrochloride.

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