Chemical effects of ferrocene and 2-ethylhexyl nitrate on a low-octane gasoline: An experimental and numerical RCM study

An in-depth understanding of fuel additives chemical effects is crucial for optimal use or additive design dedicated to more efficient and cleaner combustion. This study aims at investigating the effect of an organometallic octane booster additive named ferrocene on the combustion of a low-octane gasoline at engine-relevant conditions. Rapid compression machine experiments were carried out at 10 bar, from 675 to near 1000 K for stoichiometric (Φ = 1) and lean (Φ = 0.5) mixtures. The neat surrogate fuel was a blend of toluene and n-heptane whose research octane number was 84. The doping level of additive was set at 0.1% molar basis. Ferrocene does not show a remarkable effect on the 1st- stage ignition but presents a strong inhibiting effect on the main ignition of the surrogate fuel at both equivalence ratios. The inhibiting effect increases with temperature within the investigated range. The negative temperature coefficient (NTC) behavior of the surrogate fuel is enhanced by ferrocene. A kinetic model developed by literature data assembly as well as a novel sub-mechanism involving the formation of alcohols from the reactions of iron species is proposed. The kinetic model developed simulates the inhibiting effect of ferrocene reasonably well at both equivalence ratios. Thanks to the validated kinetic model, the chemical effect of ferrocene on the fuel combustion is explored and compared with 2-ethylhexyl nitrate (EHN), which is a conventional reactivity enhancer. Three major differences between the two additives were identified: the high-temperature stability of the fuel additive, the influence of additive on the toluene reactivity and the effect of the additive on the NTC behavior. The results presented in this study contribute to the in-depth comprehension of chemical effect of two fuel additives (ferrocene and EHN) having opposite effects on fuel reactivity.     

Gorenstein n-X-Injective and n-X-Flat Modules with Respect to a Special Finitely Presented Module

Let R be a ring,X a class of R-modules and n ≥ 1 an integer.We intro-duce the concepts of Gorenstein n-X-injective and n-X-flat modules via special finitely presented modules.Besides,we obtain some equivalent properties of these modules on n-X-coherent rings.Then we investigate the relations among Gorenstein n-X-injective,n-X-flat,injective and fiat modules on X-FC-rings (i.e.,self n-X-injective and n-X-coherent rings).Several known results are generalized to this new context.     

Label-free detection of neuron-drug interactions using acoustic and Kelvin vibrational fields

Kelvin and acoustic fields of high-frequency have been employed in the non-invasive investigation of immortalized hypothalamic neurons, in order to assess their response to different concentrations of specific drugs, toxins, a stress-reducing hormone and neurotrophic factors. In an analytical systems biology approach, this work constitutes a first study of living neuron cultures by scanning Kelvin nanoprobe (SKN) and thickness shear mode (TSM) acoustic wave techniques. N-38 hypothalamic mouse neurons were immobilized on the gold electrode of 9 MHz TSM acoustic wave devices and gold-coated slides for study by SKN. The neurons were exposed to the neurochemicals betaseron, forskolin, TCAP, and cerebrolysin. Signals were collected with the TSM in real-time mode, and with the SKN in scanning and real-time modes, as the drugs were applied at biologically significant concentrations. With the TSM, for all drugs, some frequency and resistance shifts were in the same direction, contrary to normal functioning for this type of instrument. Possible mechanisms are presented to explain this behaviour. An oscillatory signal with periodicity of approximately 2 min was observed for some neuron-coated surfaces, where the amplitude of these oscillations was altered upon application of certain neurotrophic factors. These two new techniques present novel and non-invasive electrodeless methods for detecting changes at the cellular level caused by a variety of neuroactive compounds, without killing or destroying the neurons.     

Theoretical Study of the Dimerization of Chlorophyll (a) and Its Hydrates: Implication for Chlorophyll (a) Aggregation

Dimeric structures chlorophyll (a) (Chla) and their mono‐ and dihydrated have been suggested to play an important role in the mechanism of photoreaction center chlorophyll special pairs PSI and PSII. Despite their functional importance, the molecular basis structures for interacting two Chla molecules and the structural stabilization role of H₂O in the formation of hydrated Chla dimer complexes is poorly understood. In this article, the different coordination modes between two interacting Chla molecules and the configurational (orientation and distance) features between the dimer and bound H₂O molecules are characterized by means of super molecule approach the density functional theory DFT. An estimation of the thermodynamic quantities is made for Chla dimerization and hydration processes. The results indicate that structure including ester linkages via H₂O hydrogen bonding is the most favorable conformation for the dihydrated chlorophyll (a) dimer at B3LYP/6‐31G*‐DCP level of calculation. The dispersion interaction is shown to be of great significance for the Chla dimer stabilization. In aqueous nonpolar solvent, the thermodynamics show that Chla has a slightly stronger driving force for full hydration than for dimerization and that hydration of the dimers is rather weakly exergonic. The tetrahydrated dimers having a similar arrangement to that in crystals of ethyl chlorophyllide (a) dihydrate are found to be more stable than the Chla dihydrated dimer. The data underscore the key role of H‐bonding in the stability of Chla‐H₂O adducts and, in particular, the great importance of the Chla monomeric dihydrated species in the hydration and dimerization of Chla in aqueous media. Clearly, the Chla dihydrates (Chla‐2 H₂O) are found more stable than the monohydrates (Chla‐H₂O) and the Chla dimers (Chla₂), owing to a particular structure in which cooperative interactions occur between the H₂O molecules and Chla. Calculations also indicate that the most thermodynamically preferred pathway for the formation of Chla dimer hydrates can be represented by two steps: the first corresponds to the formation of Chla monomeric dihydrates and the second is the dimerization of the dihydrates on to tetrahydrated Chla dimers. These results allow to obtain a new possible pathway for Chla dimer formation processes and could provide new insights to the aggregation of chlorophyll (a) in solution.