Low Temperature Fluidized Bed Nitriding of Austenitic Stainless Steel

In the present investigation, low temperature nitriding has been attempted on AISI 316L austenitic stainless steel by using a laboratory fluidized bed furnace. The nitriding was performed in temperature range between 400°C and 500°C. X-ray diffraction, metallography, and corrosion tests were used to characterize the resultant nitrided surface and layers. The results showed that fluidized bed process can be used to produce a precipitation-free nitrided layer characterized by the S phase or expanded austenite on austenitic stainless steel at temperatures below 500°C. But there exists a critical temperature and an incubation time for effective nitriding, below which nitriding is ineffective. The corrosion behaviour of the as-nitrided surfaces is significantly different from that previously reported for low temperature plasma nitriding. This anomaly is explained by the formation of iron oxide products and surface contamination during the fluidized proces

Measuring the electronic properties of poly-si thin film solar cells deposited on textured substrate

Electrical properties of PECVD produced poly-Si photovoltaic layers on the various textured substrates showing the light trapping effect have been investigated using an AC-conductivity technique. From temperature dependence of electron (hole) conductivities using n-i-n (p-i-p) structures, the Fermi level of the poly-Si layer on the slightly textured substrates is found to locate at the center of the band gap and this material is 'truly' intrinsic. As RMS roughness of the textured substrate, q increases, the Fermi level becomes close to conduction band edge, and finally, the poly-Si layer on the highly textured substrate exhibits n-type character even though any deposition conditions for the poly-Si layers are not changed at all. Changes in electrical conductivities of the poly-Si thin films in conjunction with the results on photovoltaic performances and microstructure are also discussed

(±)-3-[4‘-(N,N-Dimethylamino)cinnamyl]benzazepine Analogs: Novel Dopamine D1 Receptor Antagonists

Neurochemical studies and structure−activity relationships of dopamine D1 receptor ligands suggest that their intrinsic activity may depend on the conformational state or binding site at which they interact on the receptor protein. Important differences in the modes of binding of these ligands may confer their agonist, partial agonist, or antagonist properties. In an effort to develop novel dopamine D1 antagonists and investigate the D1 antagonist pharmacophore, a series of (±)-(N-alkylamino)benzazepines were prepared in which (±)-7-chloro-8-hydroxy-3-[6-(N,N-dimethylamino)hexyl]-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (1) demonstrated the highest binding affinity (K i = 49.3 nM) and selectivity to dopamine D1 receptors. This compound inhibited dopamine-stimulated adenylyl cyclase, in rat caudate, confirming a D1 receptor antagonist profile. From this initial series of N-alkylamino-substituted benzazepines, structure−activity relationships suggested that the terminal amino function was necessary for optimal binding affinity and selectivity at D1 vs D2 sites. Further, addition of this side chain to the D1 agonist pharmacophore (e.g., 7,8-dihydroxy-3-[4-(N,N-dimethylamino)butyl]-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine) greatly decreased binding affinity at D1 receptors. These data suggested that a binding domain that may be unique to the D1 antagonists may have been identified. In an attempt to exploit an apparent amine-accepting binding domain on the D1 receptor, a series of (±)-3-[4‘-(N,N-dimethylamino)cinnamyl]benzazepine analogs was designed and prepared, as D1 antagonists. In this series, (±)-7-chloro-8-hydroxy-3-[4‘-(N,N-dimethylamino)cinnamyl]-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (6a) showed the highest binding affinity (K i = 60.3 nM) for dopamine D1 receptors. Compound 6a was a potent dopamine D1 antagonist as evidenced by its ability to block dopamine-stimulated adenylyl cyclase activity in rat caudate (predicted K i value = 18.4 nM). Molecular modeling studies demonstrated that the most potent and selective dopamine D1 antagonists, in both series, contained terminal amino groups 8−9 Å away from the 3-position benzazepine nitrogen. Compounds that lacked a terminal amine function or where this moiety was less than 7 Å away from the benzazepine nitrogen demonstrated significantly lower binding affinities. Therefore, this series of (±)-3-[4‘-(N,N-dimethylamino)cinnamyl]benzazepines also appears to be identifying an amine-accepting binding domain on the dopamine D1 receptor protein that may be further explored for the development of novel dopamine D1 antagonists