A stochastic analysis of the coupled lateral–torsional drill string vibration

Nonlinear Dynamics - Drilling operations in the oil and gas industry present a highly complex dynamic. In this paper, the coupled lateral–torsional vibrations of a drill string are...     

Averaging of boundary-value problem in domain perforated along (<Emphasis Type="Italic">n</Emphasis> − 1)-dimensional manifold with nonlinear third type boundary conditions on the boundary of cavities

The research considers the asymptotic behavior of solutions u _? of the Poisson equation in a domain ?-periodically perforated along manifold γ = ω ∩ {x ₁ = 0} ≠ Ø with a nonlinear third type boundary condition ? _v u _? + ?^?ασ(x, u _?) = 0 on the boundary of the cavities. It is supposed that the perforations are balls of radius C ₀?^α, C ₀ > 0, α = n ? 1 / n ? 2, n ≥ 3, periodically distributed along the manifold γ with period ? > 0. It has been shown that as ? → 0 the microscopic solutions can be approximated by the solution of an effective problem which contains in a transmission conditions a new nonlinear term representing the macroscopic contribution of the processes on the boundary of the microscopic cavities. This effect was first noticed in [1] where the similar problem was investigated for n = 3 and for the case where Ω is a domain periodically perforated over the whole volume. This paper provides a new method for the proof of the convergence of the solutions {u _?} to the solution of the effective problem is given. Furthermore, an improved approximation for the gradient of the microscopic solutions is constructed, and more accurate results are obtained with respect to the energy norm proved via a corrector term. Note that this approach can be generalized to achieve results for perforations of more complex geometry.     

New Resin Acid Derivatives: Diisocyanate,Diurethanes and Diureides

New difunctional resin acids derivatives, diisocyanate, diurethanes and diureides were obtained via nitration of dehydroabietic acid followed by catalytic hydrogenation or reduction; carbonylation of the resulting amine and further reaction of the new diisocyanate with alcohols or amines.     

A Survey of Optimization by Building and Using Probabilistic Models

This paper summarizes the research on population-based probabilistic search algorithms based on modeling promising solutions by estimating their probability distribution and using the constructed model to guide the exploration of the search space. It settles the algorithms in the field of genetic and evolutionary computation where they have been originated, and classifies them into a few classes according to the complexity of models they use. Algorithms within each class are briefly described and their strengths and weaknesses are discussed.     

Antifungal activity of mango peel and seed extracts against clinically pathogenic and food spoilage yeasts

The antioxidant and antifungal (antiyeast) properties of mango (Mangifera indica) peel and seed by-products were investigated. Nine extracts were obtained using three cultivars and two extraction methods. Significant differences between cultivars and extraction methods were detected in their bioactive compounds and antioxidant activity. The antifungal property was determined using agar diffusion and broth micro-dilution assays against 18 yeast species of the genera Candida, Dekkera, Hanseniaspora, Lodderomyces, Metschnikowia, Pichia, Schizosaccharomyces, Saccharomycodes and Zygosaccharomyces. All mango extracts showed antifungal activity. The minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) values were lower for seed than for peel extracts. MICs and MFCs ranged from values <0.1 to 5 and 5 to >30 mgGAE/mL, respectively. The multivariate analysis showed a relationship between antifungal activity, the capacity to inhibit lipid peroxidation and total phenol content. These properties were associated with high levels of proanthocyanidins, gallates and gallotannins in the extracts.     

Reaction of aromatic nitroso compounds with chemical models of ‘thiamine active aldehyde’

Aromatic nitroso compounds in the presence of base and 2-(α-hydroxyalkyl)-3,4-dimethylthiazolium trifluoromethanesulfonate and related salts furnish in variable yields O- and N-acyl-aryl hydroxylamines and 3,4-dimethylthiazolium trifluoromethanesulfonate. A primary kinetic isotope effect of 4.9, obtained for the appropriate 2α-deuterated thiazolium salt, points to the C_2α-H bond cleavage as the rate determining step. Radical species detected by ESR were unambiguously identified as phenylhydronitroxide, but attempted trapping of the corresponding C-heterocyclic radicals by TEMPO was not successful, and substrates incorporating a potential cyclopropyl radical clock gave products with the cyclopropyl ring intact. Theoretical calculations revealed a large activation energy for such reaction, which thus cannot per se exclude the intervention of such radical species. Evidence for the likely operation of two concurrent mechanisms, a radical and a preponderant ionic pathway, involving the conjugate base of the thiazolium salt, as the chemical model for ‘active thiamine’, and ArNO is presented for the formation of the products of the reaction.     

Synthesis and antimalarial activity of ethyl 3‐amino‐4‐oxo‐9‐(phenylsubstituted)thieno[2,3‐b]quinoline‐2‐carboxylate derivatives

A series of thieno[ 2 ,3‐b]quinolone derivatives were synthesized and investigated for their abilities to inhibit β‐hematin formation, hemoglobin hydrolysis and in vivo for their efficacy in rodent Plasmodium berghei. Compound 3b was the most promising as inhibitor of hemoglobin hydrolysis, and its effects as inhibitor of β‐hematin formation was promising. When the aromatic ring was substituted in 2 (Me), in 3 (CF₃) or in 2,4 (Cl) the inhibition of hemoglobin proteolysis was maximal (88%), the rest of compounds maintained a low inhibition. The most active compound to emerge in vitro and in murine studies, was 3b suggesting an antimalarial activity via multiple mechanisms.