Selective nitrosation of guanazine: preparation of azidoaminotriazole and nitrosoguanazine anion-Cu(II) complexes

Guanazine (3,4,5-triamino-1,2,4-triazole) is selectively nitrosated on C-NH₂ to produce nitrosoguanazine (3-nitrosamino-4,5-diamino-1,2,4-triazole). The nitrosoguanazine is used to prepare 5-azido-3-amino-1,2,4-triazole and nitrosoguanazine anion-Cu(II) complexes.     

Polymerization products of p-benzoquinone as thermal stabilizers for rigid poly(vinyl chloride). Part II—Evaluation of the stabilizing efficiency

Quinone-tin polymers prepared by the cationic polymerization of p-benzoquinone with tin(II)chloride in the absence of solvent have been investigated as thermal stabilizers for rigid PVC at 180°C in air by measuring the rate of dehydrochlorination. The results reveal the higher stabilizing efficiency of these products relative to dibutyltin maleate, basic lead carbonate and barium-cadmium stearate stabilizers commonly used in industry. The induction period in the early stages of the dehydrochlorination process increases as a function of the metal content in the stabilizer molecule. The evidence indicates that the quinone and the metal part (

) of the stabilizer participate in the stabilization process by trapping the radical intermediates, as well as blocking the odd electron sites formed on the PVC chains. The mechanism of stabilization suggested to account for the results obtained supports a radical mechanism for the dehydrochlorination reaction.     

Tilting up iterated tilted algebras

We show that, if is a representation-finite iterated tilted algebra of euclidean type , then there exist a sequence of algebras , and a sequence of modules , where , such that each is an APR-tilting -module, or an APR-cotilting -module, and is tilted representation-finite.

     

Nucleation of the Al6(Fe,Mn)-to-α-Al–(Fe,Mn)–Si transformation in 3XXX aluminium alloys. II. Transformation in cast aluminium alloys

The nucleation behaviour of the homogenization-induced Al₆(Fe,?Mn)-to-α-Al–(Fe,?Mn)–Si transformation is investigated in a companion paper to part I (a study with roll-bonded diffusion couples). Diffusion experiments using silicon-coated Al–0.53?wt%?Fe–1.02?wt%?Mn alloy blocks allow control of the thermodynamic driving force for transformation within a microstructure typical of a cast ingot. As expected, this microstructure appears to give ready and yet stochastic nucleation as silicon diffuses into the alloy sections. In addition, transmission electron microscopy is used to analyse partially transformed particles in heat-treated alloy samples of fixed silicon content. This confirms the suggestion made in part I that the transformation preferentially nucleates at matrix grain/cell boundaries. Nucleation theory suggests this results from the ability of the boundaries to relieve volume changes associated with the nucleation event.     

Contact mechanisms and design principles for alloyed Ohmic contacts to p-type GaN

Contact mechanisms and design principles of alloyed Ohmic contacts to p-type GaN (p-GaN) are studied. Illustrative studies include bilayer, trilayer and quadrilayer Ohmic contacts. Almost all contacts appear to follow the proposed design principles. The removal of the surface insulating layer, preferably by plasma etching, leads to metal/semiconductor barrier lowering. This, together with thermionic emission, plays a crucial role for yielding low-resistance metal/p-GaN contacts. Band-gap narrowing and/or image force lowering due to heavy doping also contribute to the low contact resistivity. A judicious choice of the layer thicknesses of appropriate metal combination, rapid thermal annealing (RTA) time, RTA temperature and RTA ambient can produce large-work-function alloy(s) in contact with the p-GaN epitaxial layer, creating a robust low-resistivity thermionic-emission-induced Ohmic contact. The fundamental physics of contact mechanisms and design principles proposed in the study is useful for making other contacts. These are general enough to be extended to other III–V nitride materials, at the least.     

On the dual-phase-lag thermoelasticity theory

The uniqueness and reciprocal theorems are proved without the use of Laplace Transforms for the Dual-Phase-Lag thermoelasticity theory. Variational principle is established for a linear anisotropic and inhomogeneous thermoelastic solid. The dissipative inequality is used to obtain a continuous dependence result for isotropic solid.     

Multiclass analysis on repaglinide,flubendazole, robenidine hydrochloride and danofloxacin drugs

The drugs under study; repaglinide (Repag), flubendazole (Flu), robenidine hydrochloride (Roben) and danofloxacin (Dano) are antidiabetic, anthelmintic, anticoccidial, and antibiotic drugs. In the present study, they are investigated using electron impact mass spectral (EI-MS) fragmentation at 70 eV, in comparison with thermal analyses measurements (TGA/DrTGA and DTA) and molecular orbital calculation (MO). Semi-empirical MO calculation, AM1 procedure, has been carried out on Repag, Flu, Roben and Dano both as neutral molecules (in TA) and the corresponding positively charged species (in MS). The calculated MO parameters include bond length, bond order, charge distribution on different atoms and heat of formation. The fragmentation pathways of Repag, Flu, Roben and Dano in EI-MS led to the formation of important primary and secondary fragment ions. The mechanism of formation of some important daughter ions can be illuminated from comparing with that obtained using mass spectrometer through the accurate mass measurement determination. The MO provides a base for fine distinction among sites of initial bond cleavage and subsequent fragmentation of drug molecules in both thermal analysis and MS techniques. The activation thermodynamic parameters, such as, (activation energy E¹), (enthalpy ΔH¹), (entropy ΔS¹) and (Gibbs free energy ΔG¹) are calculated from the DrTGA curves using Coats–Redfern and Horowitz–Mitzger methods.     

BSA Interaction,Molecular Docking,and Antibacterial Activity of Zinc(II) Complexes Containing the Sterically Demanding Biomimetic N3S2 Ligand: The Effect of Structure Flexibility

Two zinc(II) complexes, DBZ and DBZH₄, that have (ZnN₃S₂) cores and differ in the bridging mode of the ligating backbone, effectively bind to BSA. The binding affinity varies as DBZ > DBZH₄ and depends on the ligand structure. At low concentrations, both complexes exhibit dynamic quenching, whereas at higher concentrations they exhibit mixed (static and dynamic) quenching. The energy transfer mechanism from the BSA singlet excited state to DBZ and DBZH₄, is highly likely according to steady-state fluorescence and time-correlated singlet photon counting. Molecular docking was used to support the mode of interaction of the complexes with BSA and showed that DBZ had more energy for binding. Furthermore, antibacterial testing revealed that both complexes were active but to a lesser extent than chloramphenicol. In comparison to DBZH₄, DBZ has higher antibacterial activity, which is consistent with the binding constants, molecular docking, and particle size of adducts. These findings may have an impact on biomedicine.     

Adsorptive characteristics of some metal ions on chitosan/zirconium phosphate/silica decorated graphene oxide

Journal of Radioanalytical and Nuclear Chemistry - Graphene oxide/chitosan/zirconiumphosphate/silicate (GO/CS/ZrP/Si) as a novel nano-composite has highly adsorption of 134Cs, 60Co, 152, 154Eu and...     

Green's functions for continuously supported plates

The Green's functions for an infinite elastic plate, attached respectively to a Pasternak or a Kerr base model, and subjected to a concentrated force, are obtained in terms of Bessel functions. It is shown, that for each base model, depending on the plate and base parameters, the solutions may be of different form. The method of images is then utilized to generate closed form solutions for the semi-infinite and quarter plates with simply supported boundaries. Paper also presents a generalization of Bessel functions of the Kelvin type and a discussion of their properties. They were needed for the solution of some of the equations under consideration.Research supported by National Science Foundation Grant MSM-8308919.