Melting temperature of trans-polyoctenamer

The effect of microstructure on crystallizability of polyoctenamers prepared by R₃Al-WCl₆ catalyst was studied. The results indicate that polyoctenamers with a broad range of trans-vinylene content do crystallize. The measured melting points are dependent on the trans-vinylene content. From the dependence of melting temperature on copolymer composition, a value of 73 ± 2°C. for the melting point and a molar heat of fusion ΔH_u of 3520 cal./mole are calculated for 100% trans-polyoctenamer. From the melting point depression in the presence of diluent, a value for ΔH_u of 4800 cal./mole is obtained.     

Antifungal Activity and In Silico Studies on 2-Acylated Benzo- and Naphthohydroquinones

The high rates of morbidity and mortality due to fungal infections are associated with a limited antifungal arsenal and the high toxicity of drugs. Therefore, the identification of novel drug targets is challenging due to the several resemblances between fungal and human cells. Here, we report the in vitro antifungal evaluation of two acylphenols series, namely 2-acyl-1,4-benzo- and 2-acyl-1,4-naphthohydroquinones. The antifungal properties were assessed on diverse Candida and filamentous fungi strains through the halo of inhibition (HOI) and minimal inhibitory concentration (MIC). The antifungal activities of 2-acyl-1,4-benzohydroquinone derivatives were higher than those of the 2-acyl-1,4-naphthohydroquinone analogues. The evaluation indicates that 2-octanoylbenzohydroquinone 4 is the most active member of the 2-acylbenzohydroquinone series, with MIC values ranging from 2 to 16 μg/mL. In some fungal strains (i.e., Candida krusei and Rhizopus oryzae), such MIC values of compound 4 (2 and 4 μg/mL) were comparable to that obtained by amphotericin B (1 μg/mL). The compound 4 was evaluated for its antioxidant activity by means of FRAP, ABTS and DPPH assays, showing moderate activity as compared to standard antioxidants. Molecular docking studies of compound 4 and ADMET predictions make this compound a potential candidate for topical pharmacological use. The results obtained using the most active acylbenzohydroquinones are promising because some evaluated Candida strains are known to have decreased sensitivity to standard antifungal treatments.     

Electrochemical study of a dendritic family at the water/1,2-dichloroethane interface

The transfer of six dendritric molecules, DMs, across the water/1,2-dichloroethane interface was investigated using cyclic voltammetry. From the variation of peak potential with pH, two different mechanisms of transfer were postulated depending on the nature of the molecules. Voltammetric parameters were employed to evaluate the hydrophilic/hydrophobic character and calculate the acid dissociation constant of these molecules. The results were explained taking into account the nature and multiplicity of functional surface groups.     

Synthesis, characterization, and photoinduced energy and electron transfer in a supramolecular tetrakis (ruthenium(II) phthalocyanine) perylenediimide pentad

Metal coordination was probed as a versatile approach for designing a novel electron donor/acceptor hybrid [PDIpy(4){Ru(CO)Pc}(4)] (1), in which four pyridines placed at the bay region of a perylenediimides (PDIpy(4)) coordinate with four ruthenium phthalocyanine units [Ru(CO)Pc]. This structural motif was expected to promote strong electronic coupling between the electron donors and the electron acceptor, a hypothesis that was confirmed in a full-fledged physicochemical investigation focusing on the ground and excited state reactivities. As far as the ground state is concerned, absorption and electrochemical assays indeed reveal a notable redistribution of electron density, that is, from the electron-donating [Ru(CO)Pc] to the electron-accepting PDIpy(4). The most important thing to note in this context is that both the [Ru(CO)Pc] oxidation and the PDIpy(4) reduction are rendered more difficult in 1 than in the individual building blocks. Likewise, in the excited state, strong electronic communication is the inception for a rapid charge-transfer process in photoexcited 1. Regardless of exciting [Ru(CO)Pc] or PDIpy(4), spectral characteristics of the [RuPc] radical cation (broad absorptive features from 425 to 600 nm with a maximum at 575 nm, as well as a band centered at 725 nm) and of the PDI radical anion (780 nm maximum) emerge. The correspondingly formed radical ion pair state lasts for up to several hundred picoseconds in toluene, for example. On the other hand, employing more polar solvents, such as dichloromethane, destabilizes the radical ion pair state.     

Synthesis, morphology and specific magnetization of the electrodeposited Zn-Ni-P thin films on copper substrate from non-cyanide electrolyte

Thin films of Zn-Ni-P on a copper substrate were synthesized by electrodeposition from chloride baths. It was found that the diffraction reflections of the crystal structure of Zn-Ni-P thin layers occur at thicknesses d ≥ 5 µm. The X-ray diffraction studies results confirm the formation in the Zn-Ni-P films of ZnNi₁₀P₃ compound. The morphology of the obtained films was analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS). The films are continuous and have a typical topography with many homogeneous globular features. EDS confirmed the formation of Zn-Ni-P coating only in 2 samples with Zn:Ni:P atomic ratios of 1:8:4 and 4:8:3, respectively. X-ray Photoelectron Spectroscopy (XPS) revealed the chemistry and the thickness of the studied thin films. At room temperature and thickness d ≥ 5 µm the investigated thin layers exhibit high values of the specific magnetizations in the range (25–37) A m² kg^?1, leading to the potential use in devices, appliances and electronics. The Curie temperature values of the synthesized Zn-Ni-P films were determined. It was found that by heating Zn-Ni-P thin layers of thicknesses d ≥ 5 µm up to a temperature T=900 K an interaction was detected with the copper substrate leading to a lower specific magnetization.      

Numerical simulation for rotating internal weakly viscoelastic flows in rectangular ducts

The present work develops a numerical method for the solution of rotating internal weakly viscoelastic flows in rectangular ducts for dimensionless parameters such as the Reynolds, Rossby and Weissenberg numbers, taken respectively in the intervals between 171 and 12000, 0.047 and 1/12 and up to 1/10000. It is shown that the usual counter‐rotating double‐vortex configuration of secondary flow breaks down with the increase of the Reynolds number (over the threshold of 171). For higher Reynolds numbers such as 7500 and 12000 the secondary flow diffuses to the interior of the duct where it assumes a fully developed configuration and the transition to the turbulence structure is observed. The Sobolev norms increase almost proportionally to the increase of the Reynolds number, and play an essential role for more complex problems involving transition to turbulence modelling. Copyright © 2002 John Wiley & Sons, Ltd.     

Approximating nonequilibrium processes using a collection of surrogate diffusion models

The surrogate process approximation (SPA) is applied to model the nonequilibrium dynamics of a reaction coordinate (RC) associated with the unfolding and refolding processes of a deca-alanine peptide at 300 K. The RC dynamics, which correspond to the evolution of the end-to-end distance of the polypeptide, are produced by steered molecular dynamics (SMD) simulations and approximated using overdamped diffusion models. We show that the collection of (estimated) SPA models contain structural information "orthogonal" to the RC monitored in this study. Functional data analysis ideas are used to correlate functions associated with the fitted SPA models with the work done on the system in SMD simulations. It is demonstrated that the shape of the nonequilibrium work distributions for the unfolding and refolding processes of deca-alanine can be predicted with functional data analysis ideas using a relatively small number of simulated SMD paths for calibrating the SPA diffusion models.     

A photochemical on-off switch for tuning the equilibrium mixture of H2 nuclear spin isomers as a function of temperature

The photochemical interconversion of the two allotropes of the hydrogen molecule [para-H(2) (pH(2)) and ortho-H(2) (oH(2))] incarcerated inside the fullerene C(70) (pH(2)@C(70) and oH(2)@C(70), respectively) is reported. Photoexcitation of H(2)@C(70) generates a fullerene triplet state that serves as a spin catalyst for pH(2)/oH(2) conversion. This method provides a means of changing the pH(2)/oH(2) ratio inside C(70) by simply irradiating H(2)@C(70) at different temperatures, since the equilibrium ratio is temperature-dependent and the electronic triplet state of the fullerene produced by absorption of the photon serves as an "on-off" spin catalyst. However, under comparable conditions, no photolytic pH(2)/oH(2) interconversion was observed for H(2)@C(60), which was rationalized by the significantly shorter triplet lifetime of H(2)@C(60) relative to H(2)@C(70).