Size-based analysis of incinerator fly ash using gravitational SPLITT fractionation, sedimentation field-flow fractionation, and inductively coupled plasma-atomic emission spectroscopy

Fly ash has been regarded as hazardous because of its high adsorption of toxic organic and/or inorganic pollutants. Fly ash is also known to have broad distributions of different chemical and physical properties, such as size and density. In this study, fly ash emitted from a solid waste incinerator was pre-fractionated into six sub-populations by use of gravitational SPLITT fractionation (GSF). The GSF fractions were then analyzed by sedimentation field-flow fractionation (SdFFF) and ICP–AES. SdFFF analysis showed the fly ash has a broad size distribution ranging from a few nanometers up to about 50 µm. SdFFF results were confirmed by electron microscopy. Inductively coupled plasma–atomic emission spectroscopy (ICP–AES) analysis of the GSF fractions showed the fly-ash particles contain a variety of inorganic elements including Ca, Si, Mg, Fe, and Pb. The most abundant in fly ash was Ca, followed by Si then Mg. No correlations were found between trace element concentration and particle size.     

Chemical and thermal stability of alkanethiol and sulfur passivated InP(100)

InP(100) surfaces treated with Na2Sx9H20 and CnH(2n+1)SH are examined by contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy to determine the chemical and thermal behavior of these passivated surfaces. The surfaces coated by octadecanethiol (n = 18) self-assembled monolayers (SAMs) are found to be more stable toward oxidation than the S-passivated surface. The chemical stability of octadecanethiol SAMs in various environments is examined. The thiol monolayer is found to be stable in 0.1 M HCl but degrades in 0.1 M NaOH, boiling chloroform, and water. The behavior of these surfaces at elevated temperatures under a vacuum is also investigated. The octadecanethiol-coated InP(100) is stable up to 473 K, above which the films begin to degrade. Unlike other substrates on which the entire molecule including the sulfur headgroup desorbs together, on InP, the sulfur headgroup remains on the surface even after annealing to 673 K. These observations suggest that the desorption occurs by S-C bond cleavage as well as In-S bond cleavage. The sulfur of S-passivated InP is found to be more thermally stable than that of the octadecanethiol monolayer, perhaps due to their different bonding geometries and hence energies.     

Arbophylline, a novel heptacyclic indole with a cage skeleton incorporating an acetal moiety

A new indole alkaloid, arbophylline, possessing a novel heptacyclic cage skeleton, and incorporating an acetal function, was obtained from the Malayan Kopsia arborea. The structure was established by spectroscopic analysis and a possible biogenetic pathway from an akuammiline-type precursor is presented.     

Nuclear Coordinate dependence of electronic transition moments in orbitally forbidden transitions: A new interpretation of deuterium isotope effects

The nuclear coordinate dependence of electronic transtion moments has been investigated for the purpose of finding new interpretations of deuterium isotope effects on spectral intensities and radiative decay rates in orbitally forbidden electronic transitions. By using “AO following nuclei” wavefunctions as the building block for the electronic wavefunction in the adiabatic BO vibronic wavefunction, the spin-free hamiltonian is diagonalized to generate eigenfunctions and eigen-energies. It is found that the electronic transtion moments based on these eigenfunctions show dependences upon the vibrational modes which are not directly involved in vibronic coupling. This leads to interpretations of the deuterium isotope effects in T₁ → S₀ radiative transitions of aromatic hydrocarbons and S₀ → S₁ absorption in pyrazine which are not based on the conventional Herzberg—Teller or non-BO coupling.     

Electronic relaxation of molecular exciplexes in the vapor phase

Interaction of electronically excited TCNB (tetracyanobenzone) and ground-state MB (methylated benzenes) leads to the formation of fluorescent exciplexes in the vapor phase. Studies of exciplex fluorescence as a function of excess vibrational energy in TCNB and of temperature and pressure of added buffer gas, lead to the conclusion that the low-frequency inter-molecular vibrations play a very important role in the radiationless deactivation of exciplexes. The results also indicate that collisional relaxation of low-frequency intermolecular vibrations proceeds much more rapidly than that of high-frequency intramolecular vibrations.     

Sample enrichment by using monolithic precolumns in microcolumn liquid chromatography

An on-line sample enrichment system was designed using monolithic precolumns in microcolumn LC. The monolithic ODS capillary columns were prepared via in situ sol-gel processes. The enrichment efficiency of the monolithic columns was tested by using phthalates as the analytes. The relative standard deviations (n = 6) for the retention time, peak area and peak height were between 0.4 and 1.2%, 0.9 and 5.5% and 0.4 and 3.9%, respectively. The system was linear (R2 > 0.99) within the working sample concentration and sample volume ranges. Comparing to 0.2 microl injection with a typical sample injector, the theoretical plate number of a same separation column was increased by 3-6-fold when the precolumn unit was used for sample injection. The recoveries of the analytes were between 88 and 120%, and the sample volume that could be injected into the system was increased up to 5000-fold. The limits of detection were improved by more than 2000-fold and were between 0.21 and 0.87 ng ml(-1) even with a UV absorbance detector. This system was applied to the determination of phthalates contained in laboratory distilled water and tap water samples.     

Differential effects of Fas cross-linking on phospholipase D activation and related lipid metabolism in Fas-resistant A20 cells

A20 murine lymphoma cells undergoing Fas-mediated apoptosis showed increase in the activity of phospholipase D (PLD), which is involved in proliferative or mitogenic cellular responses. Using A20 cell lines that were resistant to Fas-induced apoptosis, we investigated the differential effects of Fas cross-linking on PLD activity and sphingolipid metabolism. The basal PLD activities in all of the selected three Fas-resistant clones (#5, #8, and #11) were about 2~4 folds higher than that of wild type A20 cells. Among the PLD isoforms, PLD2 expression was increased in all of the selected Fas-resistant clones. The Fas downstream signaling events triggered by Fas cross-linking, including the activations of PLD, phosphatidylcholine-specific phospholipase C (PC-PLC), sphingomyelinase (SMase), the increase in diacylglycerol (DAG) and protein phosphorylation levels, and the translocation of protein kinase C to membrane were not changed in both of Fas-resistant clone #5 and #8. In contrast, Fas cross-linking stimulated the activity of PLD, PC-PLC, and SMase, translocation of PKC, and protein phosphorylation in Fas-resistant clone #11, similar to that of wild type cells. We also found that clone #11 had a different Fas sequence encoding Fas B which has been known to inhibit Fas-induced apoptosis. These findings suggest that increased PLD2 expression resulting in increased basal PLD activity and the blockade of Fas downstream signaling cascades may be involved to limit apoptosis induced by Fas cross-linking.     

The Vroman effect: a molecular level description of fibrinogen displacement

The molecular level details of the displacement of surface adsorbed fibrinogen from silica substrates were studied by atomic force microscopy, immunochemical assays, fluorescence microscopy, and vibrational sum frequency spectroscopy. The results showed that human plasma fibrinogen (HPF) can be readily displaced from the interface by other plasma proteins near neutral pH because the positively charged alpha C domains on HPF sit between the rest of the macromolecule and the underlying surface. The alpha C domains make weak electrostatic contact with the substrate, which is manifest by a high degree of alignment of Lys and Arg residues. Upon cycling through acidic pH, however, the alpha C domains are irreversibly removed from this position and the rest of the macromolecule is free to engage in stronger hydrogen bonding, van der Waals, and hydrophobic interactions with the surface. This results in a 170-fold decrease in the rate at which HPF can be displaced from the interface by other proteins in human plasma.     

Non self-consistent field theory

Roothaan's SCF method [2] is reformulated so that two non-SCP methods are developed to solve the eigenequation. The results from these methods can be used as starting eigenfunctions for Roothaan's SCF method.

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Zusammenfassung Die self-consistent field Methode von Roothaan [2] wird neu formuliert: dabei werden zwei Nicht-SCF Methoden zur Lösung der Eigenwertgleichung entwickelt. Deren Resultate können als Anfangsfunktionen bei Rechnungen mit der SCF-Methode von Roothaan benutzt werden.

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Résumé La méthode SCF de Roothaan [2] est reformulée en développant deux méthodes non-SCF pour la solution de l'équation aux valeurs propres. Les résultats de ces deux méthodes peuvent être utilisées comme fonctions de départ pour la méthode SCF de Roothaan.

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The title Theoretical Chemistry has been transferred to the Division of Physical Chemistry.