Selective Analysis of Sulfur-Containing Species in a Heavy Crude Oil by Deuterium Labeling Reactions and Ultrahigh Resolution Mass Spectrometry

A heavy crude oil has been treated with deuterated alkylating reagents (CD₃I and C₂D₅I) and directly analyzed without any prior fractionation and chromatographic separation by high-field Orbitrap Fourier Transform Mass Spectrometry (FTMS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) using electrospray ionization (ESI). The reaction of a polycyclic aromatic sulfur heterocycles (PASHs) dibenzothiophene (DBT), in the presence of silver tetrafluoroborate (AgBF₄) with ethyl iodide (C₂H₅I) in anhydrous dichloroethane (DCE) was optimized as a sample reaction to study heavy crude oil mixtures, and the reaction yield was monitored and determined by proton nuclear magnetic resonance spectroscopy (¹H-NMR). The obtained conditions were then applied to a mixture of standard aromatic CH-, N-, O- and S-containing compounds and then a heavy crude oil, and only sulfur-containing compounds were selectively alkylated. The deuterium labeled alkylating reagents, iodomethane-d₃ (CD₃I) and iodoethane-d₅ (C₂D₅I), were employed to the alkylation of heavy crude oil to selectively differentiate the tagged sulfur species from the original crude oil.     

Hydrierende Vergasung von Kohle – Neuere Betriebsergebnisse

Hydrogasification of coal – recent operational results . The Rheinische Braunkohlenwerke AG has built and has been operating a semi-technical pilot plant for hydrogasification of coal in a fluidized bed. The objective is to develop a coal gasification process with hydrogen for producing directly substitute natural gas. Between 1976 and 1981, the semitechnical pilot plant having a capacity of 100 kg C/h was operated for about 22,900 h under test conditions, more than 9,500 h of which were under gasification conditions. During this time, approximately 1,400 metric tons of dry coal were gasified. The longest coherent operational phase under gasification conditions was 748 h in which 86.4 metric tons of dry lignite were gasified. Carbon gasification rates up to 82% and methane contents in the dry raw gas (free of N₂) up to 48 vol.-% were obtained. A detailed evaluation of the test results provided information on the influence of additional parameters on the efficiency dates of the gasifier and a considerable refining of the results obtained previously. Moreover, several components were tested for which no operational experience had previously been gained; these were newly developed devices, e. g. the inclined tube for feeding coal into the fluidized bed. Within the framework of scale-up work to large-scale coal gasification plants, a pilot plant having a capacity of approximately 6 t C/h will be commissioned in late 1982.     

The high-conductance state of cortical networks

We studied the dynamics of large networks of spiking neurons with conductance-based (nonlinear) synapses and compared them to networks with current-based (linear) synapses. For systems with sparse and inhibition-dominated recurrent connectivity, weak external inputs induced asynchronous irregular firing at low rates. Membrane potentials fluctuated a few millivolts below threshold, and membrane conductances were increased by a factor 2 to 5 with respect to the resting state. This combination of parameters characterizes the ongoing spiking activity typically recorded in the cortex in vivo. Many aspects of the asynchronous irregular state in conductance-based networks could be sufficiently well characterized with a simple numerical mean field approach. In particular, it correctly predicted an intriguing property of conductance-based networks that does not appear to be shared by current-based models: they exhibit states of low-rate asynchronous irregular activity that persist for some period of time even in the absence of external inputs and without cortical pacemakers. Simulations of larger networks (up to 350,000 neurons) demonstrated that the survival time of self-sustained activity increases exponentially with network size.     

The influence of virtual presence: Effects on experienced cognitive load and learning outcomes in educational computer games

Does the immersive design of an educational gaming environment affect learners’ virtual presence and how much do they learn? Does virtual presence affect learning? This study tries to answer these questions by examining the differences in virtual presence and learning outcomes in two different computer-based multimedia environments: a gaming environment with high immersive design vs. hypertext learning environment with low immersive design. As the main focus, the effect of virtual presence on learning is also explained and tested. By identifying virtual presence as a variable that may determine learning, it is argued that computer gaming environments present a new challenge for researchers to investigate, particularly, the effects of virtual presence on the immersive design of games in order to help designers to predict which instructional configurations will maximize learning performance. In general, results revealed that the high-immersive gaming environment leads to the strongest form of virtual presence but also decreased learning. Although regression analyses indicate that virtual presence positively influences trivial- and non-trivial learning outcomes, learners who learned in a low-immersive environment outperformed the gaming group. A mediation analysis showed that the relation between virtual presence and non-trivial learning outcomes is partly mediated through increased cognitive load.     

4Pi-confocal images with axial superresolution

We present two-photon excitation 4Pi-confocal images of clustered fluorescence beads demonstrating three-dimensional far-field light microscopy with unprecedented resolution. For an excitation wavelength of 760 nm, the lateral and axial resolution amounts to 200 and 145 nm, respectively. The four-fold improved axial resolution is achieved by engineering the point-spread function through a suitable combination of aperture enlargement, two-photon excitation, confocalization and three-point deconvolution. In contrast to their confocal counterparts, 4Pi-confocal images do not exhibit the typical axial elongation. The axial resolution in the 4Pi-confocal images corresponds to about one-fifth of the wavelength and surpasses the lateral resolution by 25%.     

Quantenchemische MNDO-, AM1-, und PM3-Untersuchungen von α-D-Glucose-acetaten, -benzoaten und -(trichlor)acetaten als Modelle für die entsprechenden Amyloseverbindungen

Quantum Chemical MNDO-, AM1-, and PM3-Studies of α-D -Glucose Acetates, -Benzoates and -(Trichloro)Acetates as Models for the Respective Amylose Compounds. Heats of formation have been calculated for α-D-Glucose and also for its mono-, di- and trisubstituted derivatives (acetates, benzoates and (thrichloro)acetates in the positions 2, 3 and 6), applying the semiempirical quantum chemical methods MNDO, AM1 and PM3. When only one hydroxyl is substituted, the thermodynamic probability of generation decreases as 6>3>2 (acetates), 2>6>3 (benzoates) and 6>2>3 ((thrichloro)acetates). Generation of glucose monoacetate increases the reactivity of acetylation for both of the other OH groups. That was not established for benzoates and (trichloro)acetates. For comparison, the heats of formation have been calculated for all unbranched dodecanols and also for their acetates, benzoates and (trichlor)acetates. Enthalpies of reaction were estimated for all considered compounds taking into account the corresponding acid chlorides, one molecule of pyridine and the generation of pyridinium hydrochloride. It was shown that, generally, the reactivity of the dodecanols is higher than that of unsubstituted and substituted glucose. The results are discussed with regard to preparative application.     

Evolution of maturity levels of the particle surface and bulk during soot growth and oxidation in a flame

We performed a study of the evolution of soot composition and fine structure, i.e., maturity level, in an atmospheric ethylene-air diffusion flame. We used laser-induced incandescence (LII) to provide information about maturity level of the bulk primary particle and X-ray photoelectron spectroscopy (XPS) to provide complementary information about particle-surface-maturity level. The results demonstrate that the bulk material and the particle surface evolve separately in the flame. Increased soot-maturity level is associated with increased long-range order of the particle fine structure. This increased order leads to an increase in the absorption cross-section in the visible and near-infrared and a shift of the absorption to longer wavelengths with increasing maturity level of the bulk particle. These trends result in a decrease in the dispersion exponent (?) and increase in the absorption cross-section scaling factor (?), as inferred from LII measurements. LII measurements demonstrate that bulk-maturity level increases with height-above-the-burner (HAB) until it reaches a plateau in the center of the flame at the maximum in the soot volume fraction. Bulk-maturity level only slightly decreases as soot is oxidized at larger HABs. Increased maturity level also leads to an increase in long-range sp² hybridization. XPS measurements of the sp²/defect ratio demonstrate an increase in soot surface-maturity level with increasing HAB, but the surface-maturity level increases more gradually with HAB than the bulk-maturity level. Whereas the bulk-fine-structure order decreases slightly in the oxidation region, the surface order decreases dramatically, indicating that oxidation occurs preferentially at the surface under these conditions.

Copyright © The Authors. Published with license by American Association for Aerosol Research