A novel dual surface modification on titanium in dental use: Characterization and topography

This laboratory study aimed to compare, contrast, and evaluate the effect of a novel dual surface modification method on the adhesion strength of resin composite cement to titanium. C.p.-2 grade titanium samples were silica-coated, etched with HNO₃(69vol %) or a blend of HCl (35vol %) and H₃PO₄ (85vol %), for 1 h at 80°C. Surface roughness was measured by surface roughness profilometry, topographic analysis by scanning electron microscopy (SEM), atomic force microscopy (AFM), and surface analyses by energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS). Silanization of all specimens was carried out after SEM, EDX, and AFM analysis, before enclosed mold microshear bond strength testing (EM-μSBS). Adhesion strengths were measured after artificial ageing: 1 day, 1 week, 4 weeks, and 8 weeks by EM-μSBS testing and failure mode analysis by optical microscopy. Polished titanium was used as a control. The highest surface roughness was observed in titanium samples treated with silica-coating + HCl-H₃PO₄ etching. The elemental composition confirmed the presence of Ti, O, C, with Si and Al in samples treated with silica-coating. A gradual decrease in EM-μSBS values was observed in all titanium samples with adhesive and cohesive failure modes. The novel dual surface modification method applied in this study suggests that silica-coating + HCl-H₃PO₄etching strongly affects titanium surface topography and roughness. The presence of Si on silica-coated surface modified titanium before silanization with an experimental silane has a positive effect on the EM-μSBS of titanium samples treated with silica-coating only or silica-coating + HNO₃ etching.     

Tautomerism of 2-arylamino- and 2-benzylaminothiazoline

It was established by means of the IR, UV, and PMR spectra that 2-arylamino-4,4-dialkyl-5-methylenethiazolines have the 2-aryliminothiazolidine structure in the crystalline state and in solutions, whereas the 2-benzylamino derivatives can exist in both the amino and imino forms.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 755–760, June, 1979.     

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

Magnetic ordering temperatures in heavy rare earth metal dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to a pressure of 69 GPa and a temperature of 10 K. Previous studies using magnetic susceptibility measurements at high pressures were able to track magnetic ordering temperature only till 7 GPa in the hexagonal close packed (hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. This is followed by a rapid increase in the magnetic ordering temperatures in the double hcp phase and finally leveling off in the distorted face centered cubic phase of Dy. Our studies reaffirm that 4f-shell remains localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.     

Ab Initio Study of the (DMF) m · (HCl) n (m,n = 0–2) Complexes

Based on the results of ab initio calculations (B3LYP, 6-31++G(d,p)), the structures and stability of the complexes DMFA · HCl, (DMF)₂ · HCl, DFF · (HCl)₂, and (DMF · HCl)₂ are compared. In the complex with a 1 : 1 composition, DMF and HCl form a hydrogen bond of the molecular type. In the heterotrimers with compositions 1 : 2 and 2 : 1, the hydrogen bond noticeably strengthens. In the tetramer (DMF · HCl)₂, the most pronounced proton transfer takes place and two quasi-symmetric hydrogen bridges O···H···Cl are formed and stabilize this complex. The results of calculations are compared with data on the structure of complexes between HCl and DMF obtained by crystal-structure XRD and vibrational spectroscopy in solutions.     

Formation and aqueous surface wettability of polysiloxane nanofibers prepared via surface initiated, vapor-phase polymerization of organotrichlorosilanes

The formation of high aspect ratio organosiloxane fibers of nanodimensionality via the surface-induced vapor-phase polymerization of vinyltrichlorosilane is reported. We also demonstrate the versatility of our method by producing fibers of various densities, polydispersities, and lengths. Nanofibers were characterized using SEM, EDX, XPS, TOF-SIMS, and variable-angle FTIR. Advancing aqueous contact angle measurements were used to evaluate the nanofiber surface wettability.     

Increasing efficiency of photoelectronic conversion by encapsulation of photosynthetic reaction center proteins in arrayed carbon nanotube electrode

The construction of efficient light energy converting (photovoltaic and photoelectronic) devices is a current and great challenge in science and technology and one that will have important economic consequences. Here we show that the efficiency of these devices can be improved by the utilization of a new type of nano-organized material having photosynthetic reaction center proteins encapsulated inside carbon nanotube arrayed electrodes. In this work, a generically engineered bacterial photosynthetic reaction center protein with specifically synthesized organic molecular linkers were encapsulated inside carbon nanotubes and bound to the inner tube walls in unidirectional orientation. The results show that the photosynthetic proteins encapsulated inside carbon nanotubes are photochemically active and exhibit considerable improvement in the rate of electron transfer and the photocurrent density compared to the material constructed from the same components in traditional lamella configuration.     

Association of Molybdenum Ionic Species with Alumina Surface

The adsorption isotherms at 25, 45, and 65 degrees C of molybdenum solutions of concentration ranges between 10(-3) and 3x10(-2) M(Mo) (pH 4-5) on different alumina samples are investigated. The analysis is conducted using a modified Frumkin isotherm which takes a more realistic account of the lateral interaction between adsorbed species and considers that the adsorption takes place on the most basic OH groups on the surface of alumina. The results are discussed in view of the difference in solutions speciation, and the changes in the pH of the remaining supernatant solutions. The solution temperature, PZC of the used aluminas, the configuration of the basic OH groups on their surface, and the pore structure have been shown to intervene effectively. Copyright 2000 Academic Press.     

On-line procedures for the phase-transfer-catalyzed dansylation of phenolic steroids — Application to biological samples

Summary Commercially available equipment from two manufacturers served to set up an automated system for the precolumn phase-transfer-catalyzed dansylation of phenolic steroids, using ethynyl estradiol (EE) and estradiol (E) as model compounds. Using different mixing techniques, the on-line determination of EE and E in 200l untreated urine samples was achieved at a rate of 3–8 analyses per hour. Detection limits were calculated to be 3–5 ng/ml. Calibration curves in urine were linear over two orders of magnitude with r=0.999 (n=5) for EE and r=0.999 (n=6) for E. The repeatability of the determination of EE in urine (1g/ml) was 3.9% (RSD; n=20) and of E (1.5l/ml) 3.8% (RDS; n=10). The use of plasma instead of urine in the on-line procedures was not possible due to rapid formation of emulsions, but E and EE were determined in 100l plasma samples using a mild off-line mixing procedure in 10min. Detection limits were calculated to be ca 10ng/ml.A reaction detector, based on a solvent-segmented system, was developed for the on-line post-column dansylation of phenols and was coupled with a reversed-phase LC system. The highly selective system showed excellent linearity over at least two orders of magnitude with r=0.9999 (n=6) for both phenol and 2,5-dimethylphenol. The reproducibility was good with RSD values of around 2%. Detection limits for loop injections from standard solutions were calculated to be between 4 and 11ng.