Cyclopentadiene evolution during pyrolysis-gas chromatography of PMR polyimides

The effect of formulated molecular weight (FMW), extent of cure, and cumulative aging on the amount of cyclopentadiene (CPD) evolved from Polymerization of Monomeric Reactants (PMR) polyimides were investigated by pyrolysis-gas chromotography (PY-GC). The PMR polyimides are additional crosslinked resins formed from an aromatic diamine, a diester of an aromatic tetracarboxylic acid and a monoester of 5-norbornene-2, 3-dicarboxylic acid. The PY-GC results were related to the degree of crosslinking and to the thermo-oxidative stability (weight loss) of PMR polyimides. Thus, PY-GC has shown to be a valid technique for the characterization of PMR polyimide resins and composites via correlation of the CPD evolved versus the thermal history of the PMR sample

What are the key issues regarding the role of geothermal energy in meeting energy needs in the global south?

Globally, the potential of geothermal far exceeds that of all other renewable sources together, although investment in the other sources to date has far exceeded investment in geothermal. World Energy Assessment estimates in 2000 for the global potential of all renewables (EJ/yr) were Geothermal 5000, Solar 1575, Wind 640, Biomass 276, Hydro 50, giving a total of 7541 (UNDP, 2000). When installed, geothermal plants have a far higher capacity factor than other sources (solar depends on the level of direct insolation, wind power on wind, etc.); estimates (REN21, 2009) give wind-power 21%, solar PV 14% but geothermal is at least as high as 75% and often more than 95%, given that once a plant is established it operates continuously except for routine down-time for maintenance and rare break-downs

Differential Muon Tomography to Continuously Monitor Changes in the Composition of Subsurface Fluids

Muon tomography has been used to seek hidden chambers in Egyptian pyramids and image subsurface features in volcanoes. It seemed likely that it could be used to image injected, supercritical carbon dioxide as it is emplaced in porous geological structures being used for carbon sequestration, and also to check on subsequent leakage. It should work equally well in any other application where there are two fluids of different densities, such as water and oil, or carbon dioxide and heavy oil in oil reservoirs. Continuous monitoring of movement of oil and/or flood fluid during enhanced oil recovery activities for managing injection is important for economic reasons. Checking on leakage for geological carbon storage is essential both for safety and for economic purposes. Current technology (for example, repeat 3D seismic surveys) is expensive and episodic. Muons are generated by high- energy cosmic rays resulting from supernova explosions, and interact with gas molecules in the atmosphere. This innovation has produced a theoretical model of muon attenuation in the thickness of rock above and within a typical sandstone reservoir at a depth of between 1.00 and 1.25 km. Because this first simulation was focused on carbon sequestration, the innovators chose depths sufficient for the pressure there to ensure that the carbon dioxide would be supercritical. This innovation demonstrates for the first time the feasibility of using the natural cosmic-ray muon flux to generate continuous tomographic images of carbon dioxide in a storage site. The muon flux is attenuated to an extent dependent on, amongst other things, the density of the materials through which it passes. The density of supercritical carbon dioxide is only three quarters that of the brine in the reservoir that it displaces. The first realistic simulations indicate that changes as small as 0.4% in the storage site bulk density could be detected (equivalent to 7% of the porosity, in this specific case). The initial muon flux is effectively constant at the surface of the Earth. Sensitivity of the method would be decreased with increasing depth. However, sensitivity can be improved by emplacing a greater array of particle detectors at the base of the reservoir

Vertical effective stress as a control on quartz cementation in sandstones

Temperature-controlled precipitation kinetics has become the overwhelmingly dominant hypothesis for the control of quartz cementation in sandstones. Here, we integrate quantitative petrographic data, high spatial resolution oxygen isotope analyses of quartz cement, basin modelling and a kinetic model for quartz precipitation to suggest that the supply of silica from stress-sensitive intergranular pressure dissolution at grain contacts is in fact a key control on quartz cementation in sandstones. We present data from highly overpressured sandstones in which, despite the current burial temperature of 190 °C, quartz cement occurs in low amounts (4.6 ± 1.2% of bulk volume). In situ oxygen isotope data across quartz overgrowths suggest that cementation occurred over 100 Ma and a temperature range of 80–150 °C, during which time high fluid overpressures resulted in consistently low vertical effective stress. We argue that the very low amounts of quartz cement can only be explained by the low vertical effective stress which occurred throughout the burial history and which restricted silica supply as a result of a low rate of intergranular pressure dissolution at grain contacts

Tetrakis(ferrocenylethynyl)ethene:synthesis, spectro)electrochemical and quantum chemical characterisation

Tetrakis(ferrocenylethynyl)ethene (1) has been prepared in four steps from ethynyl ferrocene (2). In a dichloromethane solution containing 10–1 M NBu4[PF6], only a single oxidation process is observed by cyclic voltammetry, corresponding to the independent oxidation of the four ferrocenyl moieties. However, in dichloromethane containing 10–1 M NBu4[BArF4] electrolyte, where [BArF4]– is the weakly associating anion [B{C6H3(CF3)2-3,5}4]–, four distinct oxidation processes are resolved, although further spectroelectrochemical investigation revealed essentially no through bond interaction between the individual ferrocenyl moieties. Quantum chemical treatment of 1 identified several energetic minima corresponding to different relative orientations of the ferrocenyl moieties and the plane of the all-carbon bridging fragment. Further computational investigation of the corresponding monocation [1]+ supported the notion of charge localisation with no evidence for significant through bond electronic interactions

The depositional settings of organic-rich shale in the faulted lacustrine basin: A case study of the Y1 Member of the Yingcheng Formation in the Songliao Basin

Volcanic activity is often associated with the development of faulted lacustrine basins. Organic-rich shale in such basins usually contains abundant volcanic material. The influence of volcanic input on organic-rich shale deposition in the basin studied has not been discussed in detail. Based on the ten shale samples from three wells, this study analyzed the depositional environment of the Yingcheng Formation shale in the Lishu Fault Depression area of the Songliao Basin by using interpretation of logging, total organic carbon analysis, gas chromatography mass spectrometry analysis, and trace element analysis. The impact of fault break to basement and volcanic materials on the organic matter enrichment was evaluated. The results show that the organic matter of Ying 1 (Y1), the First Member of the Yingcheng Formation, in the Lishu Fault Depression is characterized mainly by type I kerogen. The shale of the Y1 Member, having high total organic carbon content, is laterally continuous and could be considered as a potential target for shale oil exploration. The shale with high total organic carbon was deposited in a freshwater deep lake under an anoxic environment. There is a significant input of volcanic material, especially around the Su2 well near the Sangshutai Fault. This study has established a sedimentary model of organic-rich shale in the faulted lacustrine basin affected by volcanic activity, which has significance for the exploration of shale oil in faulted lacustrine basins

Sandwich and half-sandwich metal complexes derived from cross-conjugated 3-methylene-penta-1,4-diynes

The cross-conjugated ethynyl–vinylidene [Ph2CvC(CuCH){C(H)vCRu(PPh3)2Cp}]PF6 ([4a]PF6), and [FcC (H)vC(CuCH){C(H)vCRu(PPh3)2Cp}]PF6 ([4b]PF6), and ethynyl–alkynyl Ph2CvC(CuCH){CuCRu(PPh3)2Cp} (5a), and FcC(H)vC(CuCH){CuCRu(PPh3)2Cp} (5b) compounds (Cp = η5-cyclopentadienyl) have been prepared from reactions of the known 3-methylene-penta-1,4-diynes Ph2CvC(CuCH)2 (3a) and [FcCHvC(CuCH)2] (3b) with [RuCl(PPh3)2Cp]. The compounds derived from 3b incorporating the more electron-rich alkene proved to be unstable during work-up, and attempts to prepare bis(ruthenium) complexes from 3a and 3b or from transmetallation reactions of the bis(alkynylgold) complex FcCHvC(CuCAuPPh3)2 (7) with RuCl(PPh3)2Cp were unsuccessful. The related bis- and tris(ferrocenyl) derivatives Ph2CvC(CuCFc)2 (6a) and FcCHvC(CuCFc)2 (6b) were more readily obtained from Pd(II)/Cu(I) catalysed cross-coupling reactions of FcCuCH with the 1,1-dibromo vinyl complexes PhCvCBr2 (1a) and FcC(H)vCBr2 (1b). Cyclic voltammetry of 6a and 6b using n-Bu4N[PF6] as the supporting electrolyte shows broad, overlapping waves arising from the sequential oxidation of the ferrocenyl moieties in electronically and chemically similar environments. Electrostatic effects between the ferrocenyl moieties are enhanced in solutions of the weakly ion-pairing electrolyte n-Bu4N[B{C6H3(CF3)2-3,5}4], leading to better resolution of the individual electrochemical processes. The comparative IR spectroelectrochemical response of 6a and 6b suggest the vinyl ferrocene moiety in 6b undergoes oxidation before the ethynyl ferrocene fragments. There is no evidence of electronic coupling between the metallocene moieties and [6a]+, [6b]n+ (n = 1, 2) are best described as Class I mixed-valence compounds

Probabilistic Determination of the Role of Faults and Intrusions in Helium‐Rich Gas Fields Formation

Natural gas fields with economic helium (>0.3 He %) require the radioactive decay of crustal uranium (U) and thorium (Th) to generate He and tectonic/structural regimes favorable to releasing and concentrating He. An unknown is determining the role of faults and structural features in focusing deep‐seated He sources on shallow accumulations. We tested the correlation between high‐He wells (n = 94) and structural features using a new high‐resolution aeromagnetic survey in the Four Corners area, USA. A depth‐to‐basement map with basement lineaments/faults, an intrusion map, and a flattened basement structural high map were created using Werner deconvolution algorithms by combining magnetic, gravity, and topography data with magnetic and gravity depth profiles. We show quantitatively (via analysis of variance) that a non‐random process controls the relationship between He (>0.3%) and both basement faults and intrusions: 88% of high‐He wells occur <1 km of basement faults; and 85% of high‐He wells occur <1 km of intrusions. As He % increases, the distance to the structural features decreases. Strong spatial/statistical correlations of He wells to both basement faults and intrusions suggest that advective transport via faults/intrusions facilitates He migration. The role of gas phase buoyancy and structural trapping is confirmed: 88% of high‐He occurs within basement structural highs, and 91% of the remaining wells are <1 km from intrusions (potential structural high). We present a composite figure to illustrate how a probabilistic approach can be used as a predictive model to improve He exploration success by targeting zones of intersection of basement faults and intrusions within basement structural highs