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The effect of alloying elements like Ti, Al, Cr, V and Mo on the oxidation resistance of Nb at high temperature (between 700 °C and 1400 °C) has been studied. The value of the parabolic oxide growth constants, [MATH], depends on the nature and morphology of oxides formed in the external scale. The growth of protective oxides, like alumina, requires a high content of alloying elements, which usually means a lower melting point and the formation of brittle phases.

The present experiments investigated the role of neurokinin-1 (NK1) and neurokinin-3 (NK3) receptors on the activity of the locus coeruleus (LC)-noradrenergic system by using a dual probe microdialysis technique in anesthetized guinea pigs. The local application in the LC of the selective NK1 receptor agonists [SAR⁹,Met(O2)¹¹]-SP (10 μM) and septide (1 μM) as well as the selective NK3 receptor agonist senktide (1 μM), enhanced the extracellular norepinephrine (NE) levels in the prefrontal cortex. The enhancing effect of [SAR⁹,Met(O2)¹¹]-SP was completely blocked by the peripheral administration of the selective non peptide NK1 and NK3 receptor antagonists, GR 205171 (1 mg/kg, i.p.) and SR 142801 (0.1 mg/kg, i.p.), respectively, whereas SR 142806 (0.1 mg/kg, i.p.) the inactive enantiomer of SR 142801 had no effect. Moreover, the [SAR⁹,Met(O2)¹¹]-SP-induced increase in LC DOPAC concentrations, is only antagonized by GR 205171. In contrast, only SR 142801 (0.3 mg/kg, i.p.) could block stereoselectively the senktide-evoked increase in NE levels. Both [SAR⁹,Met(O2)¹¹]-SP and senktide effects were blocked by local infusion into the LC of SR 142801 (10⁻⁹ M). These results demonstrate that stimulation of NK1 and NK3 receptors located in the LC area modulates the activity of the LC-NE system, and that the excitatory effects of NK1 receptor agonists require NKB/NK3 receptor activation in the LC. Synapse 43:62–69, 2002. © 2001 Wiley-Liss, Inc.

The present experiments investigated the role of neurokinin‐1 (NK1) and neurokinin‐3 (NK3) receptors on the activity of the locus coeruleus (LC)‐noradrenergic system by using a dual probe microdialysis technique in anesthetized guinea pigs. The local application in the LC of the selective NK1receptor agonists [SAR9,Met(O2)11]‐SP (10 μM) and septide (1 μM) as well as the selective NK3receptor agonist senktide (1 μM), enhanced the extracellular norepinephrine (NE) levels in the prefrontal cortex. The enhancing effect of [SAR9,Met(O2)11]‐SP was completely blocked by the peripheral administration of the selective non peptide NK1and NK3receptor antagonists, GR 205171 (1 mg/kg, i.p.) and SR 142801 (0.1 mg/kg, i.p.), respectively, whereas SR 142806 (0.1 mg/kg, i.p.) the inactive enantiomer of SR 142801 had no effect. Moreover, the [SAR9,Met(O2)11]‐SP‐induced increase in LC DOPAC concentrations, is only antagonized by GR 205171. In contrast, only SR 142801 (0.3 mg/kg, i.p.) could block stereoselectively the senktide‐evoked increase in NE levels. Both [SAR9,Met(O2)11]‐SP and senktide effects were blocked by local infusion into the LC of SR 142801 (10−9M). These results demonstrate that stimulation of NK1and NK3receptors located in the LC area modulates the activity of the LC‐NE system, and that the excitatory effects of NK1receptor agonists require NKB/NK3receptor activation in the LC. Synapse 43:62–69, 2002. © 2001 Wiley‐Liss, Inc.

Diamond-like-carbon (D.L.C.) films are characterized by a low friction coefficient, a high wear resistance and a high corrosion resistance. D.L.C. films can be obtained by P.V.D., C.V.D. and duplex techniques with solid or gaseous precursors. Depending on the processing, hydrogen concentration ranges between 0 and 60%In this study, hydrogenated D.L.C. has been deposited with a radio frequency system (13.56 MHz) onto a steel substrate. Wear was studied by pin-on-disc testing at room temperature with an alumina counterpart. Interrupted tests were carried out to go into wear mechanisms. Debris were collected after various given sliding times for transmission electron microscopy (T.E.M.) in addition to scanning electron microscopy (S.E.M.) applied to the wear tracks.

The optical absorption spectra in the energy range 0·2-5 eV of anodic oxide films and of diamond-like films (the latter being deposited either by low-energy ion implantation or by sputtering) were investigated by spectroscopic ellipsometry. The paper emphasizes first the difficulty of interpreting the data obtained on complex amorphous systems, consisting of mixtures at the nanometre level of silicon oxide + hydroxide + nitride groups or of C sp3 + C sp2 + C: H, without the full determination of their composition and concentration gradients. On the basis of the most complete analysis which could be performed by using ion-beam techniques (back-and recoil scattering, nuclear reactions, secondary-ion emission), spectroscopic ellipsometry gave valuable information about the effect of dopants on the diffusion processes in silica and also of radiation damage on the formation of amorphous diamond. It was shown for instance that the oxidation of silicon nitride proceeds essentially from the outward diffusion of Si and N, the amounts of N and vacancies of the order of 1% in the oxide being almost the only causes of the increase of electric field and growth kinetics with respect to those of pure silica. Contrary to previous assertions, the preferential sputtering of sp2-bonded C at implantation energies in the 100 eV range is not the best way to increase the percentage of sp3-bonded (diamond-like) material in amorphous films. Films obtained at an energy of 2 keV exhibited absorption properties more characteristic of a semiconductor (with a gap of 0·7 eV) than the previous films or sputtered films, without containing amounts of H which would make them susceptible to the modification of their properties. This result confirmed the previous identification of diamond-like C in 2 keV films, or correspondingly of graphite-like C in others, by soft X-ray emission.

Friction and wear of TiN, TiCN and diamond-like carbon (DLC) films were studied experimentally using a ball-on-disk tribometer. The rider was a ball of 100C6 steel or polycrystalline alumina. Two steel substrates with different hardnesses were used (250 and 880 HV).