Enamines of 1,3-dimethylbarbiturates and their symmetrical palladium(II) complexes: synthesis,characterization and biological activity

Transition Metal Chemistry - Three 1,3-dimethylbarbiturate-enamine derivatives and their symmetrical palladium(II) complexes were prepared and characterized by spectroscopic methods. In addition,...     

Selfadjoint extensions of a singular differential operator

In this work, firstly in the Hilbert space of vector-functions all selfadjoint extensions of the minimal operator generated by linear singular symmetric differential expression with a selfadjoint operator coefficient A in any Hilbert space H, are described in terms of boundary values. Later structure of the spectrum of these extensions is investigated.     

Modified Burgers-Reimschuessel model for moisture-sensitive polymers

Viscoelastic properties of moisture-sensitive polymers can be significantly affected by moisture in the ambient environment, resulting in drastic changes in the properties as the absorbed moisture content increases. In this article, a simple yet important modification to the Reimschuessel model is introduced by considering both plasticization and anti-plasticization induced by water molecules. The proposed model is validated against the results of four different polymers obtained by Onogi et al., which demonstrates its capability of describing the available data. This model can be used to estimate the performance and service life of products produced using moisture-sensitive polymers. It also reveals that small amounts of diffused moisture might have a stiffening effect on the mechanical properties of hydrophilic polymers.     

Interactions of Imidazolium Based Ionic Liquids with Water Studied by Density and Speed of Sound Measurements: Effect of the Chain Length of an Alkyl Substituent on the Imidazolium Ion

Densities and speeds of sound of three ionic liquids (ILs), 1-ethyl-3-methyl imidazoliumtetrafluoroborate (C₂mimBF₄), 1-butyl-3-methylimidazoliumtetrafluoroborate (C₄mimBF₄) and 1-hexyl-3-methylimidazoliumtetrafluoroborate (C₆mimBF₄) were measured in aqueous solutions at (288.15, 293.15, 298.15, 303.15 and 308.15) K. These data were used to calculate the volumetric properties apparent molar volume and apparent molar isentropic compression as a function of molality. Infinite dilution values for these properties were evaluated by an extrapolation procedure based on Redlich–Meyer type equations. Apparent molar isobaric expansions at infinite dilution were also obtained from the slopes of the apparent molar volume at infinite dilution versus temperature. All these properties are interpreted in terms of IL–water interactions. The hydrolysis of the \( {\text{BF}}_{4}^{ - } \) anion of the ILs and its effects on the results is discussed.     

A study on theoretical predictive model and experimental findings of melt-electrospinning process

The current study extends a previous work published by the authors in which an analytical predictive model is proposed to simulate the melt-electrospinning process. The analytical model is specifically designed to predict the various behaviors of the melt-electrospun fiber under different material and processing conditions. A brief discussion of this model is presented here to establish context and help the reader capture the modeling philosophy employed. The current study complements the previous work by focusing on the experimental aspects of the research. Correlations between the independent process parameters and the topological attributes of the melt-electrospun fibers are investigated and compared with findings from the theoretical model. The effects of changes in the process parameters on average fiber diameters and the collection diameter are experimentally analyzed using the design of experiments (DOE) techniques. Toward this end, polylactic acid (PLA) is melt-electrospun at different treatment levels of the processing parameters in a controlled environment. Two regression-based models—one for predicting the collection diameter and the other for the fiber diameter—are derived from the DOE data for benchmarking and quantitative evaluation of the predictive performance of the theoretical model. The theoretical model is run based on the same treatment levels as the experiment. The elastic parameter values used in the theoretical simulation are extracted from rheological tests. Comparison between the simulated and the observed fiber characteristics revealed that the collector diameter predictions by the theoretical model exhibited approximately a 16.7% difference compared to 24.2% for the average fiber diameter. Finally, a discussion is presented on the challenges and potential factors contributing to the observed differences. Overall, given the identified challenges and gaps in material characterization, the results of the theoretical predictive model are encouraging.     

A novel bidentate ligand containing oxime,hydrazone and indole moieties and its BF2+ bridged transition metal complexes and their efficiency against prostate and breast cancer cells

In this study, a novel bidentate ligand containing oxime, hydrazone, and indole moieties and its BF₂⁺-bridged transition metal complexes [Ni(II), Cu(II), and Co(II)] were synthesized and their cytotoxic activities against prostate and breast cancer cells were investigated. The vic-dioxime ligand bearing indole–hydrazone side groups was synthesized by reacting antiglyoximehydrazine (GH₂) with 3-methoxy indole. The ligand forms mononuclear complexes with a metal-to-ligand ratio of 1:2 with M = Co(II)(H₂O)₂, Ni(II), and Cu(II). These metal complexes were then reacted with BF₃(C₂H₅)₂O to obtain BF₂⁺-bridged transition metal complexes. The Co(II) complex of the ligand is proposed to be octahedral with water molecules as axial ligands, whereas the Ni(II) and Cu(II) complexes are proposed to be square planar. Spectral studies showed that the ligand bonded to the metal ion in a neutral bidentate fashion through the azomethine nitrogen atom and the imine oxime group. Structural assignments are supported by a combination of ¹H nuclear magnetic resonance (NMR), ¹³C NMR, Fourier-transform infrared, LC/MS, elemental analyses, and magnetic susceptibility testing. For determining the cytotoxic effects of the novel anticancer products, cancer cells were cultured. The antiproliferative effects were determined using the MCF-7 breast cancer and PC-3 prostate cancer cell lines. The antiproliferative effects of the products were analyzed and their apoptotic or necrotic effects were determined with the Hoechst/propidium iodide double staining method in both cancer cell lines. Paclitaxel was used as the positive control (1 μm ). The results indicated that the newly synthesized compounds are effective on both cell lines between concentrations of 5 and 40 μm and show their effects by apoptotic mechanisms. Besides, these products were found to be more effective on the MCF-7 cell line. The cytotoxic efficiency of the newly synthesized products was more than that of paclitaxel (depending on concentration), which is a chemotherapeutic agent used in cancer therapy.     

Amplitude and phase of light scattered by micro-scale aggregates of dielectric spheres: Comparison between theory and microwave analogy experiments

Light scattering is a useful diagnostic tool for characterization of particles. Direct scattering measurements for arbitrarily shaped micro-scale particles is difficult due to small-scale limitations. Microwave analogy is a convenient approach to realize such measurements as it enables realization of analogous experiments with larger model particles in a spectral domain where wavelengths are on centimeter scale. In the present study a test model analogous to light scattering by a micro-scale aggregate of dielectric spheres was constructed and experimentally characterized in the microwave regime. Measured amplitude and phase of the scattered field were compared with theoretical predictions obtained from quasi-exact multiple-scattering T-matrix method and discrete dipole approximation (DDA). Excellent agreement demonstrates the validities of both the experiment and the models.     

In Situ Electrochemical Production of Metal-organic Hybrid Composite Film from Nickel Containing Polyoxometalate and 3,4-Ethylenedioxy-thiophene for Sensor Application

In situ electrochemical synthesis of an organic-inorganic hybrid material composed of poly(3,4-ethylenedioxythiophene) (PEDOT) and nickel-based Keggin type polyoxometalate, K₇[Ni^IIINi^II(H₂O)W₁₁O₃₉].15H₂O(NiPOM), has been proposed here. The remarkable optical and electrical properties of the PEDOT and the unique redox properties of NiPOM have synergistically combined to make the hybrid structure highly desired multi-functional materials for a myriad of applications. The driving force for the formation of hybrid structure is thought to be electrostatic interactions between POM anions and cationic polaron/bipolaron structures that in the PEDOT. PEDOT/NiPOM based hybrid composite modified graphite electrode has been used for non-enzymatic glucose sensor platform as a sample of applications. Furthermore, PEDOT/NiPOM based sensor platform was successfully utilized for detection of glucose content with the lowest detection limit in real samples like honey and milk. These results suggest that PEDOT/NiPOM metal-organic hybrid composite could be utilized as multi-functional material for a myriad of applications.     

Effects of structural isomerism on solution behaviour of solutes: Apparent molar volumes and isentropic compression of catechol,resorcinal, and hydroquinone in aqueous solution at T = (283.15, 293.15, 298.15, 303.15, and 313.15) K

Effects of structural isomerism on solution behaviour of dihydroxybenzenes were examined through the determination of volumetric properties such as apparent molar volumes, apparent molar isentropic compressions, and isobaric expansions. The isomers were 1,2-dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), and 1,4-dihydroxybenzene (hydroquinone). The volumetric properties were determined from accurate density and speed of sound measurements at T = (283.15, 293.15, 298.15, 303.15, and 313.15) K and at various concentrations. Values at infinite dilution of these parameters were obtained by suitable extrapolation procedures. The results are discussed in terms of hydrophobic, hydrogen bonding, and dipole–dipole interactions between the three isomers and water. Catechol was found to have the strongest hydrophilic and the weakest hydrophobic interactions with water among the three isomers.     

Viscosities, Apparent Molar Volumes, Expansivities and Isentropic Compressibilities of some Fatty Acids and their Triglycerides in Benzene at (20, 30, 40 and 60) °C

Viscosities, apparent molal volumes, compressibilities and expansivities of lauric, palmitic and stearic acids and their triglycerides, trilaurin, tripalmitin and tristearin, were determined in benzene at 20, 30, 40 and 60 °C. Accurate density and sound velocity measurements carried out simultaneously with a high-precision vibrating-tube densimeter and sound velocity measuring device were utilized in deriving volume, compressibility and expansivity data. Viscosities were measured with Ostwald type viscometers. Infinite dilution values of the apparent molal volumes and compressibilities were obtained by an extrapolation procedure. Apparent molal expansivities at infinite dilution were obtained from the temperature dependence of the apparent molar volume at infinite dilution. The properties at infinite dilution were evaluated in terms of solute-solvent interactions. Volumetric results in benzene were compared with the corresponding data estimated from group contributions in aqueous solutions using the additivity rule.