A new simple synthesis of poly(thiophene-methine)s

Acid-promoted polycondensation of 3,4-(ethylenedioxy)thiophene-2-carbaldehyde leads to a conjugated heavily p-doped poly(thiophene-methine), which can be dedoped leading to a low band-gap neutral polymer.     

Study on the normalized Laplacian of a penta-graphene with applications

Let L _n denote a linear pentagonal chain with 2n pentagons. The penta-graphene (penta-C), denoted by R _n is the graph obtained from L _n by identifying the opposite lateral edges in an ordered way, whereas the pentagonal Möbius ring is the graph obtained from the L _n by identifying the opposite lateral edges in a reversed way. In this paper, through the decomposition theorem of the normalized Laplacian characteristic polynomial and the relationship between its roots and the coefficients, an explicit closed-form formula of the multiplicative degree-Kirchhoff index (resp. Kemeny's constant, the number of spanning trees) of R _n is obtained. Furthermore, it is interesting to see that the multiplicative degree-Kirchhoff index of R _n is approximately of its Gutman index. Based on our obtained results, all the corresponding results are obtained for .     

The effect of hydration on the thermal behaviour of hydrophilic non-aqueous gels stabilised by Carbopol 974P

A thermal analysis of the effect of hydration of non-aqueous polymer-stabilised gels was investigated using differential scanning calorimetry (DSC). The interaction of water with the polymer and its distribution within the gel are critical to the physicochemical behaviour of the gel, and consequently affects the utility of the gel matrix as a drug delivery vehicle. Addition of water at levels up to and including 50% (w/w) did not result in an observable freezing event in the thermogram. However, at 60 and 80% (w/w) water, phase transitions were observed, the magnitude of which were found to be independent of the annealing time within the range used. The observed melting enthalpies increased as the water concentration increased for all formulations, but were always smaller than that of pure water. There was no evidence of multiple transitions that might be attributed to different populations of water molecules. However, the results demonstrate that DSC can be employed to differentiate between freezable and non-freezable water, in these particular formulations.     

Microbial transformation of dehydroepiandrosterone

Transformation of dehydroepiandrosterone (DHEA) (1) was carried out by a plant pathogen Rhizopus stolonifer, which resulted in the production of seven metabolites. These metabolites were identified as 3beta,17beta-dihydroxyanandrost-5-ene (2), 3beta,17beta-dihydroxyandrost-4ene (3), 17beta-hydroxyandrost-4-ene-3-one (4), 3beta,11-dihydroxyandrost-4-ene-17-one (5), 3beta,7alpha-dihydroandrost-5-ene-17-one (6), 3A,7alpha,17beta-trihydroxyandrost-5-ene (7) and 11beta-hydroxyandrost-4,6-diene-3,17-dione (8). The structures of the transformed products were determined by the spectroscopic techniques.     

Exploring Amantadine Derivatives as Urease Inhibitors: Molecular Docking and Structure–Activity Relationship (SAR) Studies

This article describes the design and synthesis of a series of novel amantadine-thiourea conjugates (3a–j) as Jack bean urease inhibitors. The synthesized hybrids were assayed for their in vitro urease inhibition. Accordingly, N-(adamantan-1-ylcarbamothioyl)octanamide (3j) possessing a 7-carbon alkyl chain showed excellent activity with IC₅₀ value 0.0085 ± 0.0011 µM indicating that the long alkyl chain plays a vital role in enzyme inhibition. Whilst N-(adamantan-1-ylcarbamothioyl)-2-chlorobenzamide (3g) possessing a 2-chlorophenyl substitution was the next most efficient compound belonging to the aryl series with IC₅₀ value of 0.0087 ± 0.001 µM. The kinetic mechanism analyzed by Lineweaver–Burk plots revealed the non-competitive mode of inhibition for compound 3j. Moreover, in silico molecular docking against target protein (PDBID 4H9M) indicated that most of the synthesized compounds exhibit good binding affinity with protein. The compound 3j forms two hydrogen bonds with amino acid residue VAL391 having a binding distance of 1.858 Å and 2.240 Å. The interaction of 3j with amino acid residue located outside the catalytic site showed its non-competitive mode of inhibition. Based upon these results, it is anticipated that compound 3j may serve as a lead structure for the design of more potent urease inhibitors.     

Hydrocarbons and aromatic hydrocarbons in groundwater surrounding an earthen waste disposal pit for produced water in the Duncan oil field of New Mexico

Samples of groundwater and soil were collected from test pits placed 25 m intervals on five axes extending from an earthen waste disposal pit for produced water near the San Juan River of northwest New Mexico. Samples were obtained at depths of 1.2 to 1.5 m and were analyzed using GC and GC/MS techniques for purgable hydrocarbons, including benzenes, and for solvent extractable organic compounds. Water samples from test pits down-gradient from the disposal pit contained purgable and extractable hydrocarbons that were similar to contents of the waste disposal pit. In contrast, water samples obtained from test pits up-gradient from the waste pit were free of detectable organic components. Major purgable components in the waste pit and in surrounding groundwater included saturated/unsaturated hydrocarbons and aromatic/alkylated aromatic hydrocarbons. Samples collected 25 m from the waste pit contained concentrations of all compounds greater than in samples taken at 50 m in distance on the same exis. Total concentration of purgable aromatic hydrocarbons in groundwater from test plots ranged from a high of 200 ppb at 25 m, to a low of 12 ppb at 50 m on an axis through the plume center.     

An exact solution of a quasilinear Fisher equation in cylindrical coordinates

Lie symmetry method is applied to analyse Fisher equation in cylindrical coordinates. Symmetry algebra is found and symmetry invariance is used to reduce the equation to a first-order ODE. The first-order ODE is further analysed to obtain exact solution of Fisher equation in explicit form.     

Free vibrations of randomly inhomogeneous plates

Consider a large collection of elastic rectangular plates with random inhomogeneities, but otherwise indistinguishable in any overall sense. An expression is obtained for the natural frequency, μ, of such plates, vibrating freely under simply supported boundary conditions, in the form μ = μ⁽⁰⁾ + ?μ⁽¹⁾ + ?²μ⁽²⁾ + … where μ⁽⁰⁾ is the natural frequency of a homogeneous comparison plate, ? is a small real parameter measuring the degree of inhomogeneity, and the coefficients μ⁽¹⁾, μ⁽²⁾, …, are given explicitly. By constructing geometrically a correlation function for a special type of composite plate, μ⁽¹⁾ is computed and hence, to first order in ?, the variance of μ. The paper concludes with a theorem linking the mean and variance of μ to the volume concentration and geometry of the inclusions in the plate.