Neuritin expression and its relation with proliferation, apoptosis, and angiogenesis in human astrocytoma.

Neuritin, a new member of the neurotrophic factor family, plays an important role in promoting neuronal survival, differentiation, function, and repair. However, whether neuritin is expressed in human astrocytoma and involved in their proliferation, apoptosis, and angiogenesis remains unclear. The expression of neuritin messenger RNA, protein and the relationship with proliferation, apoptosis, and angiogenesis were examined in human astrocytoma samples and three glioma cell lines by immunohistochemistry, Western blot, and quantitative real-time RT-PCR and so on. And neuritin immunoreactivity score (IRS), proliferative index (PI), apoptotic index (AI), overall daily growth (ODG), and microvessel density (MVD) in brain astrocytoma were measured. The results showed that neuritin was overexpressed in human astrocytoma samples, and the overexpression correlated positively with the malignancy of astrocytomas as reflected by changes in proliferation, apoptosis, and angiogenesis markers. In our study, we found neuritin is overexpressed in astrocytoma, which may be an important factor in tumorigenesis and progression of astrocytoma, and can be used as a target for biological therapy.

[Raman spectra of carbon fibers during electrochemical treatment].

Laser Raman spectroscopy was employed to characterize the microstructure variations of polyacrylonitrile-based carbon fibers during electrochemical treatment, and the characteristics of first-order Raman spectra of carbon fibers with different treatment time were investigated in the present paper. The results indicate that the Raman spectra of the carbon fibers can be fitted into four bands, named as D (or D1) band, G band, D2 band and D3 band, respectively. The Raman parameters to characterize surface microstructure variations of carbon fibers mainly include R(I(D2)) / I(G), area ratio of D band and G band), I(D2) / I(G) (area ratio of D2 band and G band), I(D3) / I(G) (area ratio of D3 band and G band), and I(D(S))/ I(G) (area ratio of all the disordered structure and G band). The peak separation between D band and G band becomes large after electrochemical treatment. R increases, which indicates that the surface disordered degree of carbon fibers increases. I(D3) / I(G) increases, which is caused by organic molecules, fragments or functional groups; decreases which is caused by the break of the aliphatic structures. With increasing treatment time, I(D(S)) / I(G) increases continuously, and the change trend of l(D(S)) / I(G) is consistent with that of R value, which can be used to comprehensively explain the variation of the surface structure of carbon fibers. So, the variety rules of the structure of carbon fibers can be investigated by laser Raman spectroscopy during electrochemical treatment.

[Study on spectral emissivity of C/C composites].

Different types of C/C composites were prepared by conventional molding, and the changes in normal spectral emissivity of samples were tested. The testing results show that spectral emissivity of C/C composite reinforced by short cut carbon fibers is generally higher than the sample reinforced by carbon cloth in the entire 2500-13000nm wavelength region. The structure of short cut carbon fibers is relatively loose and the number of material particles is less than other samples in unit volume, which increases the penetration depth of electromagnetic waves. This is the reason for higher normal spectral emissivity and better heat radiation property. Meanwhile, the test results of normal spectral emissivity for fiber perform and C/C composite samples show that the spectral emissivity of resin carbon is better than fiber carbon because of the difference in microstructure for the two kinds of carbon materials. Laser Raman spectroscopy was employed to analyze the microstructures of different carbon materials, and the results show that because sp3 and sp2 hybrid states of carbon atoms in resin carbon produced more vibration modes, the resin carbon also has higher normal spectral emissivity and better characteristics of heat radiation.

Property changes of powdery polyacrylonitrile synthesized by aqueous suspension polymerization during heat-treatment process under air atmosphere.

High molecular weight powdery polyacrylonitrile (PAN) polymers were prepared by aqueous suspension polymerization employing itaconic acid (IA) as comonomer and alpha,alpha(')-azobisisobutyronitrile (AIBN) as initiator at 60 degrees C. PAN polymers obtained with different monomer ratios were characterized by EA, DSC, FTIR and XRD. It is investigated that the oxygen element content in PAN polymers increased with the increase of required IA amounts in the feed and heat-treatment temperatures. DSC curves of PAN copolymers exhibited the triplet character, owing to the exothermic cyclization and oxidative reactions during heat-treatment process. Introduction of IA in the feed relaxed exothermic reactions of PAN polymers under air atmosphere. Structure and crystallinity changes were affected by required IA amounts in the feed and enhancement of heat-treatment temperatures. The characteristic functional groups (including C[triple bond]N, C=O, CH(2)) presented in FTIR spectra of PAN polymers indicated copolymerization reaction of AN and IA. Existence of some organic groups (C-O, C=C and/or C=N) indicated formation of ladderlike structure during heat-treatment process. PAN homopolymer had the better crystallinity (mainly peak intensity and peak area around 2theta = 17 degrees) than most RT-PAN copolymers. When heat-treatment temperature is around 210 degrees C, peak intensity, peak area, L(c) and CI of HT-PAN polymers corresponding to samples 1# and 2# got maxima, while crystallinity became weak at higher heat-treatment temperatures.

[Raman spectra of PAN-based carbon fibers during surface treatment].

Laser Raman spectroscopy was employed to characterize the microstructure changes of PAN based carbon fibers among different surface treatments, and the characteristics of first-order Raman spectra of carbon fibers during surface treatment were investigated in the present paper. The results show that the variety of carbon fibers' phase structures can be represented by Raman spectroscopy parameters, such as the Raman frequency shifts of main D and G bands, FWHMs and additive bands' area ratios at the positions of different Raman frequency shifts. During different surface treatment, some changes in the first-order Raman spectroscopy parameters of PAN based carbon fibers were observed, the Raman frequency shifts of D and G bands moved toward higher wavenumber, and the values of R(I(D)/I(G)) also improved, which can be used to measure the graphite crystallite size of carbon fiber. It is suggested that the graphite microstructure of carbon fibers is decomposed during surface treatment, the crystallite size is reduced, and the activity of the graphite crystallite boundary is improved. Moreover, the full-widths at half maximum (FWHM) of D and G bands both decrease, which can give information on the order of graphite microstructure and the quantity of defects in carbon fibers, and the relative bands' areas of A and D" bands also decrease, which can be attributed to the structure of amorphous carbon or some kinds of organic functional groups in carbon fibers. These differences among the spectra demonstrate that the structure of amorphous carbon in carbon fibers is easier to oxidize or decompose than multilayer graphite structure, so the relative proportion of amorphous carbon decreases during surface treatment. The conclusions obtained by Raman spectra are basically in agreement with the improvement of apparent crystallization degrees of carbon fibers during surface treatment, which were calculated by X-ray diffraction method. So the variety rules of carbon fibers' phase structures can be investigated by laser Raman spectroscopy.

Low temperature induced synthesis of TiN nanocrystals.

TiN nanocrystals were successfully prepared through the direct reaction between TiCl(4) and NaNH(2) induced at 300 degrees C. The yield based on Ti is approximately 80%. X-ray powder diffraction indicated that the product was cubic TiN with a lattice constant of a = 4.243 A. Transmission electron microscopy revealed that nanocrystalline TiN with a diameter of 10 nm or so and extremely long straight rods were synthesized. The possible formation mechanism was also proposed.