Some novel halogenated phenazine derivatives

3-Amino-10-aryl-2-arylimino-2,10-dihydrophenazines 1 undergo iodination in the 4-position of the phenazine nucleus yielding compounds which are identical with those obtained by oxidation of appropriate N-aryl-o-phenylenediamines with sodium iodate in the presence of acid. Bromination also takes place in this position but a second bromine atom enters the para-position of the arylimino moiety. The isomeric 10-aryl-3-aryl-amino-2,10-dihydro-2-iminophenazines 2 yield unstable iodo-derivatives but undergo bromination in the 1-and 4-position of the phenazine nucléus and in the ortho- and para-positions of the arylamino substituent. Preliminary chlorination experiments indicate that the substitution pattern is analogous to that established for the brominated products. The removal of bromine and iodine from the phenazine ring by reaction with a primary or secondary amine and their replacement by hydrogen rather than by the amine residue is also recorded.     

Ultrafine grain formation and coating mechanism arising from a blast coating process: A transmission electron microscopy analysis

This article examines the substrate/coating interface of a coating deposited onto mild steel and stainless steel substrates using an ambient temperature blast coating technique known as CoBlast. The process uses a coincident stream of an abrasive blast medium and coating medium particles to modify the substrate surface. The hypothesis for the high bond strength is that the abrasive medium roughens the surface while simultaneously disrupting the passivating oxide layer of the substrate, thereby exposing the reactive metal that then reacts with the coating medium. The aim of this study is to provide greater insight into the coating/substrate bonding mechanism by analysing the interface between a hydroxyapatite coating on both mild and stainless steel substrates. The coating adhesion was measured via a tensile test, and bond strengths of approximately 45 MPa were measured. The substrate/coating interface was examined using transmission electron microscopy and selected area diffraction. The analysis of the substrate/coating interface revealed the presence of ultrafine grains in both the coating and substrate at interface associated with deformation at the interface caused by particle impaction during deposition. The chemical reactivity resulting from the creation of these ultrafine grains is proposed to explain the high adhesive strength of CoBlast coatings.     

Electrical,Thermal and Optical Diagnostics of an Atmospheric Plasma Jet System

Plasma diagnostics of atmospheric plasmas is a key tool in helping to understand processing performance issues. This paper presents an electrical, optical and thermographic imaging study of the PlasmaStream atmospheric plasma jet system. The system was found to exhibit three operating modes; one constricted/localized plasma and two extended volume plasmas. At low power and helium flows the plasma is localized at the electrodes and has the electrical properties of a corona/filamentary discharge with electrical chaotic temporal structure. With increasing discharge power and helium flow the plasma expands into the volume of the tube, becoming regular and homogeneous in appearance. Emission spectra show evidence of atomic oxygen, nitric oxide and the hydroxyl radical production. Plasma activated gas temperature deduced from the rotational temperature of nitrogen molecules was found to be of order of 400 K: whereas thermographic imaging of the quartz tube yielded surface temperatures between 319 and 347 K.     

Correlating mode shapes based on the modal assurance criterion

Correlation of mode shape results has always been a difficult task. The element by element comparison approach for a pair of vectors may lead to unreasonable results if the differences between some corresponding elements of the two vectors are large. The newly implemented alternative is to correlate a pair of vectors based on the MAC coefficient of a pair of test and analysis mode shapes. This implementation has resulted in better correlation.     

Comparison of MCNP and experimental measurements for an HPGe-based spectroscopy portal monitor

The necessity to monitor international commercial transportation for illicit nuclear materials resulted in the installation of many nuclear radiation detection systems in Portal Monitors. To overcome the difficulty of innocent alarms due to a large content of natural radioactivity or medical nuclides, Department of Homeland Security (DHS) supported the writing of the ANSI N42.38 standard (Performance Criteria for Spectroscopy-Based Portal Monitors used for Homeland Security) to define the performance of a portal monitor with nuclide identification capabilities, called a Spectroscopy Portal Monitor. To accomplish the necessary performance, several different HPGe detector configurations were modeled using MCNP for the horizontal field of view (FOV) and vertical linearity of response over the detection zone of 5 meters by 4.5 meters for 661 keV as representative of the expected nuclides of interest. The configuration with the best result was built and tested. The results for the FOV as a function of energy and the linearity show good agreement with the model and performance exceeding the requirements of N42.38.     

Self-assembly of peptide porphyrin complexes: toward the development of smart biomaterials

The anionic porphyrin, meso-tetrakis(4-sulfonatophenyl)porphine, is found to tightly bind to an engineered 14-residue peptide, resulting in induced alpha-helix formation when mixed in aqueous solutions. The small porphyrin-peptide dissociation constant (2 muM) observed is related to the energetics of peptide helix formation coupled with electrostatic interactions between the anionic porphyrin and cationic residues in the coiled peptide. Analytical ultracentrifugation measurements indicate the porphyrin-peptide complexes dimerize, probably into a coiled coil, and weakly associate to form even higher order structures.     

Cell-cell contact and membrane spreading in an ultrasound trap

An ultrasonic standing wave trap [Langmuir 19 (2003) 3635] in which the morphologies of 2-D latex–microparticle aggregates, forming a pressure node plane, were characterised has been applied here to different cell suspensions with increasing order of specificity of cross-linking molecule, i.e. polylysine with chondrocytes; wheat germ agglutinin (WGA) with erythrocytes and surface receptors on neural cells. The outcome of initial cell–cell contact, i.e. whether the cells stuck at the point of contact (collision efficiency=1) or rolled around each other (collision efficiency=0), was monitored in situ by video-microscopy. The perimeter fractal dimensions (FD) of 2-D hexagonally symmetric, closely packed aggregates of control erythrocytes and chondrocytes were 1.16 and 1.18, respectively while those for the dendrititc aggregates formed initially by erythrocytes in 0.5 μg/ml WGA and chondrocytes in 20 μg/ml polylysine were 1.49 and 1.66. The FDs for control and molecularly cross-linked cells were typical of reaction-limited aggregation (RLA) and transport diffusion-limited aggregation (DLA), respectively. The FDs of the aggregates of cross-linked cells decreased with time to give more closely packed aggregates without clear hexagonal symmetry. Suspensions of neural cells formed dendritic aggregates. Spreading of inter-cellular membrane contact area occurred over 15 min for both erythrocyte and neural cell dendritic aggregates. The potential of the technique to characterise and control the progression of cell adhesion in suspension away from solid substrata is discussed.     

Poly[(methylene oxide) oligo(ethylene oxide)] vs. poly(ethylene oxide) as hosts for neodymium compounds

In view of the residual crystallinity in PEO found to limit the solubility of some Nd³⁺-compounds, amorphous PEO (aPEO) was synthesized for exploration as an alternative host. Complexation, solubility limit, morphology, and response to moisture absorption in the doped systems were investigated using FTIR, DSC, TGA, and WAXD techniques. Representing a perturbation to the structural regularity present in PEO, aPEO was found to present lower solubilities for dopants (Nd(act)₃ and Nd(acac)₃, both characterized by a weak Nd³⁺–ether oxygen interaction. On the other hand, no difference in solubility was observed for dopant Nd(NO₃)₃, characterized by a strong Nd³⁺–ether oxygen interaction. Laser interferometry was employed to assess film homogeneity of the Nd(NO₃)₃-doped systems across a 20-mm diameter, and the measured peak-to-valley distortion values were observed to be encouraging for practical applications. © 1994 John Wiley & Sons, Inc.