Synthesis,spectral characterization and crystal structure of a novel trinuclear di-n-butyltin(IV) complex with pyruvic acid-N(4)-cyclohexylthiosemicarbazone (H2PACT)

A new trinuclear di-n-butyltin(IV) complex with pyruvic acid-N(4)-cyclohexylthiosemicarbazone (H₂PACT) ligand was synthesized and characterized by elemental analyses, molar conductivity, UV–Vis, FT-IR, ¹H, ¹¹⁹Sn NMR spectroscopy and single crystal X-ray study. Single crystal X-ray diffraction data revealed that this complex was trinuclear cyclic fashion with the pyruvic acid-N(4)-cyclohexylthiosemicarbazone ligand. In the trinuclear di-n-butyltin(IV) complex, the ligand (H₂PACT) is coordinated to the central tin(IV) atoms via the carboxylato-O, the azomethine-N and the thiolato-S atoms. The trinuclear tin system is formed by the bridges through the carbonyl oxygen atom of the carboxylate moieties and making the tin atom of seven coordinated in distorted pentagonal bipyramidal geometry. Single crystal X-ray data indicates that the complex (1) crystallized in cubic system with space group I-4₃d, a = b = c = 30.3273(17) Å, α = β = γ = 90°, Z = 16, μ(MoKα) = 1.209 mm^?1, F(000) = 12,144, and final R₁ = 0.0390, wR₂ = 0.0843 for observed reflections 4582(I > 2σ(I)).     

Preparation of Cu-doped Cd0.1Zn0.9S solid solution by hydrothermal method and its enhanced activity for hydrogen production under visible light irradiation

A series of Cu-doped Cd_0.1Zn_0.9S solid solution with various amounts of Cu dopant was successfully prepared by hydrothermal method. The properties and the photocatalytic activity of the prepared samples for hydrogen production under visible light irradiation were compared to those prepared by co-precipitation method. The Cu-doped Cd_0.1Zn_0.9S samples prepared by hydrothermal method showed both improved crystallinity and photoabsorption ability as compared to the undoped sample. On the other hand, even though Cu-doped Cd_0.1Zn_0.9S prepared by co-precipitation method also showed improved photoabsorption ability in the visible light region, the samples showed poor crystallinity compared to the undoped one. With the same amount of Cu dopant, all samples prepared by hydrothermal method were found to exhibit higher photocatalytic activity for hydrogen production than the samples prepared by co-precipitation method. It was revealed that the amount of Cu dopant, crystallinity and narrow band gap energy are important factors to obtain highly active and stable photocatalysts.     

Bioactivities and Mode of Actions of Dibutyl Phthalates and Nocardamine from Streptomyces sp. H11809

Dibutyl phthalate (DBP) produced by Streptomyces sp. {"type":"entrez-nucleotide","attrs":{"text":"H11809","term_id":"876629"}}H11809 exerted inhibitory activity against human GSK-3β (Hs GSK-3β) and Plasmodium falciparum 3D7 (Pf 3D7) malaria parasites. The current study aimed to determine DBP’s plausible mode of action against Hs GSK-3β and Pf 3D7. Molecular docking analysis indicated that DBP has a higher binding affinity to the substrate-binding site (pocket 2; −6.9 kcal/mol) than the ATP-binding site (pocket 1; −6.1 kcal/mol) of Hs GSK-3β. It was suggested that the esters of DBP play a pivotal role in the inhibition of Hs GSK-3β through the formation of hydrogen bonds with Arg96/Glu97 amino acid residues in pocket 2. Subsequently, an in vitro Hs GSK-3β enzymatic assay revealed that DBP inhibits the activity of Hs GSK-3β via mixed inhibition inhibitory mechanisms, with a moderate IC₅₀ of 2.0 µM. Furthermore, the decrease in K_m value with an increasing DBP concentration suggested that DBP favors binding on free Hs GSK-3β over its substrate-bound state. However, the antimalarial mode of action of DBP remains unknown since the generation of a Pf 3D7 DBP-resistant clone was not successful. Thus, the molecular target of DBP might be indispensable for Pf survival. We also identified nocardamine as another active compound from Streptomyces sp. {"type":"entrez-nucleotide","attrs":{"text":"H11809","term_id":"876629"}}H11809 chloroform extract. It showed potent antimalarial activity with an IC₅₀ of 1.5 μM, which is ~10-fold more potent than DBP, but with no effect on Hs GSK-3β. The addition of ≥12.5 µM ferric ions into the Pf culture reduced nocardamine antimalarial activity by 90% under in vitro settings. Hence, the iron-chelating ability of nocardamine was shown to starve the parasites from their iron source, eventually inhibiting their growth.     

Magnetic properties of ferromagnetic VFe alloys near the critical concentration for ferromagnetism

Magnetic measurements on a series of FeV alloys in the composition range 29–35 at .% Fe have been interpreted in terms of a local environment model. Values for the moment and density of magnetic clusters have been determined. Good agreement is obtained between values obtained from Curie constants, and those estimated from the critical coefficients. The results may be understood in terms of a random distribution of solute atoms.     

A thermoanalytical investigation of the thermodynamic properties of tin telluride

Journal of Thermal Analysis and Calorimetry - The heats of formation and fusion of SnTe were determined in a differential thermal analysis calorimeter. Its free energy of formation was calculated...     

Performance of derivative free search ANN training algorithm with time series and classification problems

A Manhattan search algorithm to minimize artificial neural network error function is outlined in this paper. From an existing position in Cartesian coordinate, a search vector moves in orthogonal directions to locate minimum function value. The search algorithm computes optimized step length for rapid convergence. This step is performed when consecutive search is successful in minimizing function value. The optimized step length identifies favorable descent direction to minimize function value. The search method is suitable for complex error surface where derivative information is difficult to obtain or when the error surface is nearly flat. The rate of change in function value is almost negligible near the flat surface. Most of the derivative based training algorithm faces difficulty in such scenarios. This algorithm avoids derivative information of an error function. Therefore, it is an attractive search method when derivative based algorithm faces difficulty due to complex ridges and flat valleys. In case the algorithm gets into trapped minimum, the search vector takes steps to move out of a local minimum by exploring neighborhood descent search directions. The algorithm differs from the first and second order derivative based training methods. To measure the performance of the algorithm, estimation of electric energy generation model from Fiji Islands and “L-T” letter recognition problems are solved. Bootstrap analysis shows that the algorithm’s predictive and classification abilities are high. The algorithm is reliable when solution to a problem is unknown. Therefore, the algorithm identifies benchmark solution.