• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.487-488
• /
• 2008

SiOC films containing alkyl groups have a low dielectric constant because of the interaction between the C-H hydrogen bonds and the oxygen of high electro-negative atom. The Si-$CH_3$ in a void is broken by the $O_2$, therefore the strength of CH bond in Si-O-O-$CH_3$ bond increases. The Si-O-O-$CH_3$ bond is broken by nucleophilic attack due to Si atom, again. The elongation of C-H bond causes the red shift, and the compression of C-H bond causes the blue shift. Among these chemical shifts, the blue shift from $1000\;cm^{-1}$ to $1250\;cm^{-1}$ was related with the formation of pores. If the oxygen is deficient condition, the methylradicals of the electron-rich substitution group terminate easily the Si-O-Si cross-link, and the pore is originated from the cross-link breakdown due to much methyl radicals of Si-$CH_3$. The dielectric constant of the films decreases due to pore generation.

• KCI Concrete Journal
• /
• v.12 no.2
• /
• pp.31-43
• /
• 2000

The extensive usage of pretensioned prestressed concrete component in modem construe- tion as structural members mandates precise understanding of its mechanism. Especially, an adequate transfer of prestressing force from steel tendons to concrete around the end regions of the member is a critical issue. Due to the importance of the topic, several investigators have formulated equations modeling the transfer bond length based on various bonding mechanism between steel and concrete. However, the existing models are still inadequate in predicting the bond development in pretensioned prestressed concrete members. Therefore, this study presents a model of transfer bond length based on rational theory that can simulate experimental results. The model is developed into solid mechanics based structural analysis computer program. The program is validated by comparing the analysis results with experimental results of bond stress distribution, concrete strain profiles, and transfer length in pretensioned prestressed concrete members. The proposed analytical procedure in this study can be utilized as a useful tool for realistic evaluation of transfer length in pretensioned prestressed concrete members.

• Mass Spectrometry Letters
• /
• v.1 no.1
• /
• pp.5-8
• /
• 2010

In the present study, collisionally-activated dissociation (CAD) experiments were performed under low energy collision conditions in six peptides containing a disulfide bond. Fragments produced as a result of the cleavage of a disulfide bond were obtained after CAD in four peptides (bactenecin, TGF-$\alpha$, cortistantin, and linearly linked peptide, Scheme 1) with basic amino acid residues. In contrast, the CAD analysis of two peptides with no basic residue (oxytocin and tocinoic acid) rarely produced fragments indicative of cleavage of a disulfide bond. These results are consistent with the mobile proton model suggested by the McLuckey and O'air groups (ref. 22 and 23); nonmobile protons sequestered at basic amino acid residues appear to promote the cleavage of disulfide bonds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.205-205
• /
• 2007

The SiOC film of carbon centered system was prepared using bistrimethylsilylmethane and oxygen mixed precursor by the chemical vapor deposition. The chemical properties of the SiOC film were analyzed by the I-V measurement and FTIR spectra. The main bond of 950~1200 cm-1 was composed of the Si-C, Si-O-C and Si-O bonds. The leakage current of the SiOC film increased with the increasing of the carbon content, and the drift of the current was similar to the Si-O-C bond content.

• Biomedical Science Letters
• /
• v.14 no.2
• /
• pp.105-113
• /
• 2008

The objective of this study was to evaluate the influence of surface modifications on the bonding characteristics and cytotoxicity of specific titanium porcelain bonded to milling titanium and cast titanium. Milling titanium and cast titanium samples were divided into 8 test groups. These groups are as follow: i) sandblasted with particles of different size of $220{\mu}m\;and\;50{\mu}m$, ii) different sequences of sandblasting treatment and etching treatment, iii) etched with different etching solutions, and iv) preheated or not. The surface characteristics of specimens were characterized by the test of mean roughness of surface and SEM. The bond strength of titanium-ceramic systems was measured by using three-point bending test and SEM. The results show that the mean roughness of surface of sample sandblasted with $220{\mu}m$ aluminum oxide increased and bond strength were higher than sample sandblasted with $50{\mu}m$ aluminum oxide. The mean roughness of surface decreased, but the bond strength increased when the samples sandblasted with $220{\mu}m$ aluminum oxide were preheated. The sample sandblasted with $220{\mu}m$ aluminum oxide after oxidized with occupational corrosive agent I (50% NaOH, 10% $CuSO_4{\cdot}5H_2O$) and II (35% $HNO_3$, 5% HF) showed higher bond strength than sample oxidized with 30% $HNO_3$ after sandblasted with $220{\mu}m$ aluminum oxide. Group NaCuNF220SP (milling Ti: 35.3985 MPa, casting Ti: 37.2306 MPa) which was treated with occupational corrosive agent I (50% NaOH, 10% $CuSO_4{\cdot}5H_2O$) and II (35% $HNO_3$, 5% HF), followed by sandblasting with $220{\mu}m$ aluminum oxide and preheating at $750^{\circ}C$ for 1 hour showed the highest bond strength and significant differences (P<0.05). The method for modifying surface of titanium showed excellent stability of cells.

• Journal of the Korean Chemical Society
• /
• v.23 no.6
• /
• pp.339-348
• /
• 1979

The kinetics of the solvolysis of 2-furoyl chloride and 2-thenoyl chloride in $MeOH-H_2O,\;EtOH-H_2O,\;(Me)_2CO-H_2O,\;MeCN-H_2O$ and MeCN-MeOH has been investigated. The rates were faster in protic solvents than in aprotic solvents. This was caused by the bond breaking of leaving group through hydrogen-bonding solvation of protic solvents. In MeCN-M$\'{e}$OH the rate in MeOH rich solvents was faster than in MeCN rich solvents by the specific solvation of alcoholic hydrogen and there was a maximum rate of reaction at MeOH mole fraction of 0.8. The reaction rates of solvolysis were considerably slower than those of benzoyl chloride owing to the electron withdrawing effect of thienyl and furyl groups. It was concluded that solvolytic reaction proceeds via a dissociative $S_N2$ mechanism in which bond-breaking precedes bond-formation at the transition state.

• Journal of the Korean Chemical Society
• /
• v.38 no.1
• /
• pp.1-7
• /
• 1994

Semiempirical MNDO calculations are employed to study ionicity of OH groups and stability in $T_1-OH-T_2bridges(T_1$ = Al, B and $T_2$ = P, Si) such as found in aluminophosphate family($AlPO_4-5$, BAPO-5, and SAPO-5) molecular sieves. Dimeric model clusters of Al-OH-P, B-OH-P and Al-OH-Si bridges were considered. It is shown that the elongation of the T-O bond, upon replacement of Al by B, occurs preferentially by a local deformation of the Al-O-P bridge. But the elongation of the T-O bond occurs preferentially by a rotation of Al-O-Si bridge upon substitution P for Si. Also, the ionicity of OH groups and stability increase in order to B-OH-P < Al-OH-P < Al-OH-Si bridge.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.12
• /
• pp.1493-1500
• /
• 1999

The electronic transitions from the ground state to low-lying excited states of CF₃OH have been investigated using high level ab initio quantum mechanical techniques. Also the possible photodissociation procedures of CF₃OH have been considered. The highest level employed in this study is TZP CCSD(T) level of theory. The possible four low-lying excited states can result by the excitation of the lone pair electron (n) in oxygen to σ$^*$ molecular orbital in C-O or O-H bond. The vertical transition (n → σ$^*$) energy is predicted to be 220.5 kcal/mol (130 nm) at TZ2P CISD level to theory. The bond dissociation energies of CF₃OH to CF₃O +H and CF₃+OH have been predicted to be 119.5 kcal/mol and 114.1 kcal/mol, respectively, at TZP CCSD level of theory. In addition, the transition state for the unimolecular decomposition of CF₃OH into CF₂O + HF has been examined. The activation energy and energy separation for this decomposition have been computed to be 43.6kcal/mol and 5.0 kcal/mol including zero-point vibrational energy corrections at TZP CCSD(T) level of theory.ed phenols were also estimated.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.12
• /
• pp.2001-2006
• /
• 2005

Glycoproteins and glycolipids play key roles in intracellular reactions between cells and their environments at the membrane surface. For better understanding of the nature of these events, it is necessary to know threedimensional structures of those carbohydrates, involved in them. Since carbohydrates contain many hydroxyl groups which can serve both as hydrogen bond donors and acceptors, hydrogen bond is an important factor stabilizing the structure of carbohydrate. DMSO is an aprotic solvent frequently used for the study of carbohydrates because it gives detailed insight into the intramolecular hydrogen bond network. In this study, conformational properties and the hydrogen bonds in $\beta$-lactose in DMSO are investigated by NMR spectroscopy and molecular dynamics simulations. NOEs, temperature coefficients, deuterium isotope effect, and molecular dynamics simulations proved that there is a strong intramolecular hydrogen bond between O3 and HO2' in $\beta$-lactose and also OH3 in $\beta$-lactose may form an intermolecular hydrogen bond with DMSO.

• Restorative Dentistry and Endodontics
• /
• v.46 no.3
• /
• pp.32.1-32.10
• /
• 2021

Objectives: This study aimed to evaluate the effect of the application method of universal adhesives on the shear bond strength (SBS) of repaired composites, applied with different thicknesses. Materials and Methods: The 84 specimens (Filtek Z350 XT) were prepared, stored in distilled water for a week and thermocycled (5,000 cycles, 5℃ to 55℃). They were roughened using 400-grit sandpapers and etched with phosphoric acid. Then, specimens were equally divided into 2 groups; Single Bond Universal (SU) and Prime&Bond Universal (PB). Each group was subdivided into 3 subgroups according to application methods (n = 14); UC: 1 coat + uncuring, 1C: 1 coat + curing, 3C: 3 coats + curing. After storage of the repaired composite for 24 hours, specimens were subjected to the SBS test and the data were statistically analyzed by 2-way analysis of variance and independent t-tests. Specimens were examined with a stereomicroscope to analyze fracture mode and a scanning electron microscope to observe the interface. Results: Adhesive material was a significant factor (p = 0.001). Bond strengths with SU were higher than PB. The highest strength was obtained from the 1C group with SU. Bonding in multiple layers increased adhesive thicknesses, but there was no significant difference in SBS values (p = 0.255). Failure mode was predominantly cohesive in old composites. Conclusions: The application of an adequate bonding system plays an important role in repairing composite resin. SU showed higher SBS than PB and the additional layers increased the adhesive thickness without affecting SBS.