Effect of Erosive Agents on Surface Characteristics of Nano-Fluorapatite Ceramic: An In-Vitro Study

Erosive beverages cause dissolution of natural teeth and intra-oral restorations, resulting in surface characteristic changes, particularly roughness and degradation. The purpose of this study was to evaluate the surface roughness and topography of a dental ceramic following immersion in locally available erosive solutions. A total of 160 disc specimens of a nano-fluorapatite type ceramic (12 mm diameter and 2 mm thickness) were fabricated and equally distributed into two groups (n = 80) and then evenly distributed among the following five testing groups (n = 16): lemon juice, citrate buffer solution, 4% acetic acid, soft cola drink, and distilled water which served as a control. The surface roughness (Ra) and topography were evaluated using a profilometer and scanning electron microscope at baseline, 24 h, 96 h, and 168 h respectively. Data were analyzed using ANOVA and Tukey’s multiple comparisons (p ≤ 0.05). Surface changes were observed upon exposure to all acidic beverages except distilled water. Amongst all immersion media, 4% acetic acid produced the most severe surface roughness across all time periods (i.e., baseline, 24 h, 96 h, and 168 h). A statistically significant difference in the surface roughness values between all immersion media and across all four time intervals was observed. Erosive agents had a negative effect on the surface roughness and topography of the tested ceramic. The surface roughness increased with increased storage time intervals.     

Synthesis,characterization and crystal structure analysis of a novel oxo-centered mixed-metal complex containing unsaturated bridging carboxylates

A novel oxo-centered trinuclear mixed-metal carboxylate complex with unsaturated bridging ligands [Fe₂Cr(μ₃-O)(C₃H₃O₂)₆(H₂O)₃]·NO₃·4H₂O has been synthesized and characterized by means of Elemental analyses, Infrared spectroscopy and Crystal structure analysis. The compound crystallizes isotypically in the monoclinic space group type P2₁/c. In the compound, each M^(III) cation is coordinated by six O atoms from four unsaturated carboxylate groups as bridging ligands, one water molecule as the terminal ligand, and a μ₃-oxygen atom in the center of an equilateral triangle. The infrared spectra show resolved bands arising from ν_asym(COO) and ν_sym(COO) vibration of bridging carboxylate ligands along with those of ν_asym(M₂M′O) vibration in the complex. The difference between symmetrical and asymmetrical (COO) ligands indicate that the acrylate bridge is present in the structure of complex.      

Interfacial electronic structure of vanadyl naphthalocyanine on highly ordered pyrolytic graphite

We present a core and valence region spectroscopic analysis of the interfacial electronic structure of thin films of vanadyl naphthalocyanine (VONc) deposited onto highly oriented pyrolytic graphite (HOPG). X-ray photoelectron spectroscopy indicates the predominantly ionic character of the vanadyl metal center coordinated by the heterocycle and affords the bandgap in the thin VONc films. Valence band photoelectron spectroscopy points to the existence of three different adsorption geometries of VONc on the HOPG surface. The distribution of the different geometries can be systematically influenced in a simple post-deposition processing step, with an immediate effect on the interfacial electronic environment. We find spectroscopic evidence in the valence levels that VONc grows on HOPG most likely in a 2D-gas fashion rather than by nucleation and growth of islands. These data allow us to predict accurately the interface dipole in the case of a broad class of dipolar organic semiconductors, based simply on molecular dipole moment, polarizability and molecular diameter. This ability provides an important step towards rational optimization of energy level alignment in organic electronics.     

A divergent approach to highly substituted benzothiepinones and to 2,3-dihydrothieno[2,3-b]thiopyran-4-ones

The radical addition-transfer of S-(2-fluoro-phenacyl)xanthates can be used to construct rapidly benzothiepinones, including libraries of complex aza-bridged derivatives, and highly functionalized 2,3-dihydrothieno[2,3-b]thiopyran-4-ones.     

Ag3[PMo12O40]: An efficient and green catalyst for the synthesis of highly functionalized pyran‐annulated heterocycles via multicomponent reaction

A facile, efficient and eco‐friendly catalytic protocol was developed for the synthesis of medicinally important pyran‐annulated heterocycles via multicomponent reaction (MCR). Cyclocondensation of differently substituted aromatic aldehydes, malononitrile/ethyl cyanoacetate and various β‐dicarbonyl compounds in the presence of Ag₃[PMo₁₂O₄₀]?nH₂O as heterogeneous catalyst, in EtOH–H₂O, afforded diverse pyran‐fused chromene analogues. The merits observed for this approach were it being conducted via MCR, using commercially available or easily accessible starting materials in the presence of a green and easily separable heterogeneous and reusable catalyst, and affording high yields of desired products in very short reaction times with high purity in one‐pot fashion, thus providing a superior alternative approach for the synthesis of pyran‐annulated heterocycles.     

Organoplatinum(IV) tris-chelate complexes, each having a cyclic metallacarbonate ring: synthesis, characterization and kinetic studies of the formation

The complexes [Pt[(CH2)4](NN)], 1a (NN = 2,2'-bipyridine) and 1b (NN = 1,10-phenanthroline) react with 2,3-epoxypropylphenyl ether in the presence of CO2 to give tris-chelate platina(IV)cyclopentane complexes characterized by 1H and 13C NMR spectroscopy as [Pt[(CH2)4](CH2CHCH2OPhOCO2)(NN)], 2. The reactions proceed by the SN2 mechanism and the rates were independent of concentration of CO2. It is demonstrated that for 1a, the reaction proceeds 2.32 times faster than the similar reaction in which the dimethyl analog, [PtMe2(2,2'-bipyridine)], is used. The analog tris-chelate complex [Pt[(CH2)4](CH2CHPhOCO2)(phen)], 3a, was similarly synthesized.     

Determination of the effective atomic and mass numbers for mixture and compound materials in high energy photon interactions

In consideration the radiological properties of materials and studying the scattering processes in atomic and nuclear physics, the effective atomic and mass numbers is widely employed. These numbers have been calculated for any mixed or composite materials in interaction with high energy photons (Linac in radiation therapy). A pair equation in terms of these numbers is obtained. The first equation has been derived from the conservation of mass energy law and the second by minimizing the binding energy from the semiempirical mass formula (Myers and Swiatecki formula) that gives a relation between atomic and mass numbers for stable nuclei approximately. By these equations one can obtain the effective atomic and mass numbers for any compound or mixed materials uniquely. These numbers are calculated for some materials and compared with the other studies.     

Synthesis of Heterocyclic Pentavalent Phosphorus Compounds from Phosphite Derivatives and Indane-1,2,3-Trione

Reaction of trialkylphosphite derivatives with indane-1,2,3-trione proceeds smoothly at room temperature to afford the corresponding heterocyclic pentavalent [P(V)] phosphorus compounds via an intermolecular [4+1] cycloaddition reaction in excellent yields under solvent-free conditions. We also used dimethylphosphite and diethylphosphite instead of trialkylphosphites in this reaction, but the corresponding pentavalent phosphorus compounds were not isolated, and in both cases phosphate derivatives were obtained. The structures of the products were deduced from their IR, ¹H NMR, ¹³C NMR, and ³¹P NMR spectra, and mass spectrometry.     

Thermoanalytical study of linkage isomerism in coordination compounds

The non-isothermal differential scanning calorimetry (DSC) experiments revealed that linkage isomerization of both pure trans-[Co(en)₂(ONO)₂]PF₆ (dinitrito isomer) and trans-[Co(en)₂(NO₂)₂]PF₆ (dinitro isomer) occurs in the solid state at elevated temperatures. The process was found to be exothermic for the dinitrito isomer and endothermic for dinitro isomer. The pure isomers could be considered to be in metastable states at ambient temperatures which would be converted to an equilibrium mixture of both isomers (stable state) upon heating. Since the isomerization of both isomers may be described as a two stages process, the corresponding DSC peaks have been resolved into two peaks by means of nonlinear curve fitting tools of PeakFit^® software. The resolution of the peaks helped us to determine enthalpy changes of stepwise isomerization of both isomers. A first-order initial rate and Kissinger methods have been employed to estimate kinetic parameters of the stepwise isomerization reactions. The Kissinger method provided more reliable kinetic results. The high activation energy and positive entropy changes of isomerization of both isomers are considered as indication of a dissociative mechanism in solid state.     

Identification of PET radiometabolites by cytochrome P450, UHPLC/Q-ToF-MS and fast radio-LC: applied to the PET radioligands [11C]flumazenil, [18F]FE-PE2I, and [11C]PBR28

A general method is presented for the identification of radiometabolites in plasma of human and monkey subjects after administration of positron emission tomography (PET) radioligands. The radiometabolites are first produced in vitro, using liver microsomes, subsequently separated using fast radio-liquid chromatography (radio-LC), and individually collected and identified by ultra high-performance liquid chromatography/quadrupole-time of flight-mass spectrometry in MS and MS^E mode. Fast radio-LC provided superior resolution compared to conventional radio-LC, resulting in separation of a greater number of metabolites. The radiometabolites produced in vivo are then compared to and identified based on the in vitro results. This approach was applied to three PET radioligands, [¹¹C]flumazenil, [¹⁸F]FE-PE2I, and [¹¹C]PBR28, resulting in the identification of five, two, and one radiometabolites, respectively. This procedure can easily be adopted to identify the radiometabolites produced in vivo from a variety of PET radioligands.