Synthesis of arbitrary frequency domain transmitting pulses applicable to pulsed NMR instruments

The synthesis of specialized excitation waveforms for pulsed NMR spin systems is an integral part of many present-day NMR experiments. Methods in use include various types of constant amplitude rectangular rf pulse trains with controlled interpulse delay times, modulating amplitudes of the envelopes of a chain of rectangular pulses, special long pulse rectangular pulses, and recently, single sideband spectral selections for NMR imaging. This paper describes, in quantitative fashion with experimental results, analysis and implementation of a method to generate pulsed NMR excitation waveforms using AM and FM techniques which yield individual pulses with controllable frequency spectral distributions. Examples given are of simplified cases, but the extension to complex frequency distribution requirements is clear.     

Correlation of Phosphorus Adsorption with Chemical Properties of Aluminum-Based Drinking Water Treatment Residuals Collected from Various Parts of the United States

Over the past several decades, the value of drinking water treatment residuals (WTRs), a byproduct of the coagulation process during water purification, has been recognized in various environmental applications, including sustainable remediation of phosphorus (P)-enriched soils. Aluminum-based WTRs (Al-WTRs) are suitable adsorbent materials for P, which can be obtained and processed inexpensively. However, given their heterogeneous nature, it is essential to identify an easily analyzable chemical property that can predict the capability of Al-WTRs to bind P before soil amendment. To address this issue, thirteen Al-WTRs were collected from various geographical locations around the United States. The non-hazardous nature of the Al-WTRs was ascertained first. Then, their P adsorption capacities were determined, and the chemical properties likely to influence their adsorption capacities were examined. Statistical models were built to identify a single property to best predict the P adsorption capacity of the Al-WTRs. Results show that all investigated Al-WTRs are safe for environmental applications, and oxalate-extractable aluminum is a significant indicator of the P adsorption capacity of Al-WTRs (p-value = 0.0002, R² = 0.7). This study is the first to report a simple chemical test that can be easily applied to predict the efficacy of Al-WTRs in binding P before their broadscale land application.     

Effect of ultrasound on ammonium leaching of zinc from galmei ore

The effect of ultrasound on ammonium leaching of zinc from galmei has been investigated. The use of an ultrasonic field allows the leaching time to be decreased by a factor of ten on account of the decrease in the diffusion layer thickness on the surface of the galmei which has been leached.     

Studies of interfacial properties in polyepoxyde/carbon or glass fiber composites by means of microgravimetric techniques

The microweighing techniques have been chosen to analyze the interface problem of composite materials with polyepoxyde matrix and fibrous reinforcement, particularly the surface interactions and the wetting of carbon and glass fibers with some reactive groups of the organic matrix. The experimental data deal with the nature and energy of interactions, the hydrophilic or hydrophobic behaviour of the surfaces, the wetting angle. The surface of the fibers is modified by various treatments : oxidation, laying of a coating agent. The results allow to make propositions on the role of these treatments during the making of the composite and they also allow to analyze the differences between carbon and glass behaviour.     

Molecular dynamics simulation and energy minimization of O2 adsorbed on a graphite surface

Simulation studies of O₂ on graphite show that the quadrupole interaction strongly affects the orientational correlation between neighbouring molecules in the adsorbed solid. The energy minimization study shows two non-equivalent competing structures with nearest neighbours arranged parallel and at an angle of 60°. The precise value of the quadrupole moment stabilises one structure with respect to the other. For Θ = 0 the simulated structure agrees with experiment. For values of the quadrupole close to the experimental value there is a significant discrepancy between experiment and theory. This discrepancy can be understood in terms of the neglect of the magnetic forces arising from the exchange interaction. The best effective σ₀₀ is 5% higher than the value recommended by bulk solid studies. The minimum energy structure is incommensurate and molecules are aligned preferentially parallel to the surface at the coverage in this study.     

Spin-resolved photoemission study of in situ grown epitaxial Fe layers on W(110)

Spin- and angle-resolved photoemission spectroscopy of in situ grown epitaxial Fe layers on W(110) shows bulk-like behavior for more than two atomic Fe layers. For about ten and more atomic layers of Fe we find a spin polarization to be about -100% near the Fermi energy and +80 % between 1 eV and 3 eV binding energy. For the bilayer of Fe drastic changes in the spin-resolved spectra and a 20 % enhancement of the spin polarization compared to the bulk value are observed. The monolayer of Fe is ferromagnetically ordered with a spin polarization reduced by about 50%. A switching of the easy magnetization axis from [001] to [11̄0] is observed in the spin polarization with decreasing Fe layer thickness near d = (65±5) Å.     

D3-trishomocubanetrione synthesis and optical resolution

A large-scale synthesis for the title compound rac-1 based on 11-oxahexacyclo-[5.4.1.0^2,6.0^3,10.0^4,8.0^9,12] dodecan-5-one (12) as the key intermediate and an efficient procedure for the optical resolution of rac-1 via the diastereomeric ketals with (R,R)-2,3-butandiol are reported. The absolute configuration is established by correlating the optically pure (+)-trione ([α]_D +949°) with (-)-trishomocubane.