The adsorption of methanethiol and benzenethiol on Ag(111) and Ag(100) surfaces is studied respectively, employing ASED (Atom Superposition and Electron Delocalization) method. Metal surfaces are modelled by 3-layer clusters. The corresponding thiolate anions are taken as adsorbates. The highly coordinated binding sites are most favored for both surfaces. The tilted angles of C-S axis from the surface normal are nearly zero. There's Charge transfer from adsorbate to substrate and the stretching frequency of C-S bond upon adsorption is blue-shifted from its gas phase counterpart, and its amount is the smallest at most highly coordinated site. FMO (Fragment Molecular Orbital) analysis of the system give the explanation for these results.

The optical properties of individual 3-to 14-micron diameter CdS crystalline spheres embedded in poly(methyl methacrylate) were studied using elastic scattering. The presence of well defined sharp peaks in the 550 to 600 nm elastic scattering spectra confirmed that each microcrystal acts as an optical cavity with cavity quality factors exceeding 104. Such natural resonator microcrystals should lead to greatly enhanced local field effects near the surface of CdS, quantum electrodynamic modification of optical transition rates of nearby species and altered photochemistry. Absorptive heating following high intensity laser irradiation was found to induce a transient washout of the high Q modes.

In an attempt to understand the nature of hyperthermal ion-surface collisions, noble gas ion beams (He+, Ne+, Ar+, and Xe+) are scattered from a Si(100) surface for collision energies of 20-300 eV and for 45°incidence angle. The scattered ions are mass-analyzed using a quadrupole mass spectrometer and their kinetic energy is measured in a time-of-flight mode. The scattering event for He+ and Ne+ can be approximated as a sequence of quasi-binary collisions with individual Si atoms for high collision energies (Ei > 100 eV), but it becomes of a many-body nature for lower energies, Ar+ and Xe+ ions undergo mutliple large impact parameter collisions with the surface atoms. The effective mass of a surface that these heavy ions experience during the collision increases drastically for low beam energies.

A LOGIT transformation is a method to estimate IC50 values with two arbitrary concentration data when complete dose response curves(DRCs) are not available. We propose a modified LOGIT transformation (MLOGIT) which predicts IC50 values more accurately than the conventional LOGIT method.

The conformational study on malonic acid, hydrogen malonate, malonate, malonyl methyl sulfide, and malonyl methyl sulfide anion, as the model compounds of malonyl-CoA, was carried out using the semiempirical MO methods (MNDO, AM1, and PM3) and hydration shell model. On the whole, the feasible conformations of malonic acid, hydrogen malonate, and malonate seem to be similar to each other. In malonic acid and malonate, two carboxyl groups are nearly perpendicular to the plane of the carbon skeleton, despite of different orientation of two carboxyl groups themselves. In particular, two carboxyl groups of hydrogen malonate are on the plane formed by carbon atoms with an intramolecular hydrogen bond. The calculated results on the geometry and conformation of three compounds are reasonably consistent with those of X-ray and spectroscopic experiments as well as the previous calculations. The orientation of two carbonyl groups of malonyl methyl sulfide is quite similar to that of malonic acid, but different from that of its anion. Especially, the computed probable conformations of the sulfide anion by the three methods are different from each other. The role of hydration seems not to be crucial in stabilizing the overall conformations of malonic acid, hydrogen malonate, malonate, and malonyl methyl sulfide. However, the probable conformations of the unhydrated sulfide anion obtained by the MNDO and AM1 methods become less stabilized by including hydration. The AM1 method seems to be appropriate for conformational study of malonyl-CoA and its model compounds because it does not result in the formation of too strong hydrogen bonds and significant change in conformational energy from one compound to another.

Solid solutions of Pr2-xBaxNiO4±δ with K2NiF4-type structure were prepared in air and characterized by powder X-ray diffraction, Rietveld refinements, iodometry titrations, and conductivity measurements. The range of the solid solution was 0 ≤ x < 0.5. The crystal structure changes from orthorhombic (Fmmm) for x ≤ 0.1 to pseudo-tetragonal (I4/mmm) for x ≥ 0.2. The orthorhombic structure of x=0.1 transforms to tetragonal at low temperature. The bond distances obtained from the Rietvel analyses did not vary significantly with the Ba content except that of Ni-O (parallel to the c-axis) which showed an abrupt increase from x=0.1 to 0.2. The excess oxygen content (δ) decreases from 0.241 to 0.03 with increasing substituted Ba contents within the solution range. The samples are all semiconductors at the temperature range 4 < T < 300 K.

Linear and nonlinear optical properties of CuCl nanocrystals in silica glass have been studied using low temperature absorption, degenerate four wave mixing (DFWM), and time-resolved photoluminescence spectroscopy. Assuming a spherical shape, effective radius of the CuCl quantum dots was estimated to be 2.5 nm, which is obtained from low temperature absorption data. The DFWM experiment was performed in 380-386 nm wavelength region, and the diffracted signal was measured as a function of wavelength with 1.0 nm interval. Time-resolved photoluminescence measurement was also carried out at 77 K to obtain the time response of CuCl nanocrystals. The experimental results on the large third order nonlinear optical of CuCl quantum dots are explained in terms of crystal size and oscillator strength of quantum spheres.

Surface-enhanced Raman (SER) scattering of 2-cyanonaphthalene (2-CN) has been investigated in silver sol. Addition of halide ions was needed to obtain authentic SER spectra of the molecule. The SER spectra thus obtained exhibited a slight but noticeable dependence on the kind of halide ions used. This halide-dependent spectral variation was attributed to the orientational change of molecule on silver sol surface. A possible mechanism for such an orientational change is proposed in terms of the competitive adsorption of 2-CN with halide ions on the so-called halide-specific sites.

A series of new polymers containing phenylenevinylene (PV) units were synthesized by Wittig polycondensation reaction and properties of the synthesized polymers were characterized by FT-IR and UV-visible spectroscopy, and their light-emitting properties were studied. All of the synthesized polymers were soluble in organic solvents and showed good film quality. The absorption maxima and band edges of the polymers were moved to shorter wavelength region by reducing the electron donating alkoxy groups incorporated in phenylenevinylene unit. The photo-induced emission spectra were obtained and all of the polymers revealed their emission in blue region. The observed emission maxima of the polymers were ranged from 480-495 nm.

Substituted 3-phenyl-1-silabutanes, 3-chlorophenyl-1-silabutane (1), 3-tolyl-1-silabutane (2), and 3-phenoxyphenyl-1-silabutane (3), were prepared in 68-98% yield by reduction of the corresponding substituted 3-phenyl-1,1-dichloro-1-silabutanes with LiAlH4. The dehydrogenative homopolymerization and copolymerization of the silanes were performed with Cp2MCl2/Red-Al (M=Ti, Hf) catalyst system. The molecular weights of the resulting polymers were in the of range 600 to 1100 (vs polystyrene) with degree of polymerization (DP) of 5 to 8 and polydispersity index (PDI) of 1.6 to 3.8. The monomer silanes underwent the dehydrogenative polymerization with Cp2TiCl2/Red-Al catalyst to produce somewhat higher molecular weight polysilanes compared with Cp2HfCl2/Red-Al catalyst.

Ketene (CH2CO) adsorption on Ag(111) has been studied in ultrahigh vacuum using electron energy loss spectroscopy and temperature programmed desorption. Ketene adsorbs molecularly on Ag(111) at temperatures below 126 K. The coverage increases linearly with exposure until saturation. No multilayer formation and no shift in desorption temperature with coverage were observed, indicating a lack of attractive interaction between adsorbate molecules. The desorption activation energy is estimated to be 7.8 kcal/mol by assuming first order kinetics and a pre-exponential factor of 1013 sec-1. The adsorption geometry of ketene on the surface is determined from the relative intensities of the vibrational energy loss peaks. The CCO axis of CH2CO is found to be almost parallel to (∼4°away from) the surface and the molecular plane is almost perpendicular to the surface (∼3°tilt).

We have grown GaAs epilayers by chemical beam epitaxy(CBE) using unprecracked hydrides and metal organic compounds via a surface decomposition process. This result shows that unprecracked arsine (AsH3) or monoethylarsine (MEAs) can be used in chemical beam epitaxy(CBE) as a replacement of a precracked AsH3 source in CBE. It was also found that the uptake of carbon impurity in epilayers grown using trimethylgallium(TMG) with unprecracked AsH3 or MEAs was significantly reduced compared to that in epilayers grown by CBE process employing TMG and arsenics produced from precracked hydrides. We propose a surface structural model suggesting that the hydrogen atoms play an important role in the reduction of carbon content in GaAs epilayer. Intermediates like dihydrides from hydride sources were also considered to hinder carbon atoms from being incorporated into the epilayers or to remove other carbon containing species on the surface.

Calix[6]arenes are selectively dialkylated at the lower rim and further functionalized by the aminomethylation and Claisen Rearrangement reactions. Dialkylation was conducted by the reaction of calix[6]arene and alkyl halides such as benzyl bromide, allyl bromide, ethyl bromoacetate, propyl bromide, and methyl iodide under the carefully controlled reaction conditions. Aminomethylation was carried out with the treatment of disubstituted calix[6]arene and secondary amine in the presence of formaldehyde. Claisen rearrangement reaction of the O-diallylcalix[6]arene produced the p-diallylcalix[6]arene.

The adsorption and decomposition of NO on a stepped Pt(111) surface have been studied using thermal desorption spectroscopy and Auger electron spectroscopy. NO adsorbs molecularly in two different states of the terrace and the step, which are distinguishable in thermal desorption spectra. NO dissociates via a bent species at the step sites on the basis of vibrational spectrum data reported previously. The dissociation of NO is an activation process : the activation energy is estimated to be about 2 kcal/mol. Increase in the NO dissociation with adsorption temperature is explained by a process controlled by diffusion of the dissociated atomic nitrogen from the step to the terrace of the surface. In addition to NO and N2, the desorption peak of N2O is observed. We conclude that the formation of N2O is attributed to surface reaction of NO and N adsorbed on the surface.

The band structure of nickel monoxide having a cation defect rock salt structure is calculated by means of the tight-binding extended Huckel method. The calculation is also made for the net charge, the DOS, the COOP, the electron density of the constituent atoms, and the O 1s binding energy shift when one of the adjacent nickel atoms is defected. It is found that the band gap near the Γ direction on the Brillouin zone is about 0.2 eV, and that all of the properties calculated including the electronic structure of the oxygen atom are more effectively affected by the surface defect than the inside one. The core O 1s binding energy shift is calculated by the use of valence potential method and the results are very satisfactory in comparison with the XPS experimental findings.

A topological theory is introduced to extend Tsenoglou's theory to polymer blends having temporary and permanent networks composed of multicomponent polymers which have miscible and flexible chains. The topological theory may estimate the values of free elastic energy, the molecular weight between entanglements, and the equilibrium shear moduli, and it may establish more correctly the topological relations among these physical quantities. Through such introduction of the topological theory, there can be topologically analyzed the mixing law for the rubbery plateau modulus of a fluid polymer blend, and there can be considered the topological relationship to the equilibrium modulus of an interpenetrating polymer network containing trapped entanglements and dangling segments. The theoretically predictive values are compared and show good agreement with the experimental data for several miscible polymer blends.