Computer analysis of effects of altering jet fuel properties on refinery costs and yields

This study was undertaken to evaluate the adequacy of future U.S. jet fuel supplies, the potential for large increases in the cost of jet fuel, and to what extent a relaxation in jet fuel properties would remedy these potential problems. The results of the study indicate that refiners should be able to meet jet fuel output requirements in all regions of the country within the current Jet A specifications during the 1990-2010 period. The results also indicate that it will be more difficult to meet Jet A specifications on the West Coast, because the feedstock quality is worse and the required jet fuel yield (jet fuel/crude refined) is higher than in the East. The results show that jet fuel production costs could be reduced by relaxing fuel properties. Potential cost savings in the East (PADDs I-IV) through property relaxation were found to be about 1.3 cents/liter (5 cents/gallon) in January 1, 1981 dollars between 1990 and 2010. However, the savings from property relaxation were all obtained within the range of current Jet A specifications, so there is no financial incentive to relax Jet A fuel specifications in the East. In the West (PADD V) the potential cost savings from lowering fuel quality were considerably greater than in the East. Cost savings from 2.7 to 3.7 cents/liter (10-14 cents/gallon) were found. In contrast to the East, on the West Coast a significant part of the savings was obtained through relaxation of the current Jet A fuel specifications

Properties of the redback millisecond pulsar binary 3FGL J0212.1+5320

Linares et al. (2016) obtained quasi-simultaneous g', r' and i-band light curves and an absorption line radial velocity curve of the secondary star in the redback system 3FGL J0212.1+5320. The light curves showed two maxima and minima primarily due to the secondary star's ellipsoidal modulation, but with unequal maxima and minima. We fit these light curves and radial velocities with our X-ray binary model including either a dark solar-type star spot or a hot spot due to off-centre heating from an intrabinary shock, to account for the unequal maxima. Both models give a radial velocity semi-amplitude and rotational broadening that agree with the observations. The observed secondary star's effective temperature is best matched with the value obtained using the hot spot model, which gives a neutron star and secondary star mass of $M_{\rm 1}$=1.85$^{+0.32}_{-0.26}$ $M_{\odot}$and $M_{\rm 2}$=0.50$^{+0.22}_{-0.19}$ $M_{\odot}$, respectively.Comment: 10 pages, 8 figues, accepted by MNRA

The long-term evolution of the X-ray pulsar XTE J1814-338: a receding jet contribution to the quiescent optical emission?

We present a study of the quiescent optical counterpart of the Accreting Millisecond X-ray Pulsar XTE J1814-338, carrying out multiband (BVR) orbital phase-resolved photometry using the ESO VLT/FORS2. The optical light curves are consistent with a sinusoidal variability modulated with the orbital period, showing evidence for a strongly irradiated companion star, in agreement with previous findings. The observed colours cannot be accounted for by the companion star alone, suggesting the presence of an accretion disc during quiescence. The system is fainter in all analysed bands compared to previous observations. The R band light curve displays a possible phase offset with respect to the B and V band. Through a combined fit of the multi-band light curves we derive constraints on the companion star and disc fluxes, on the system distance and on the companion star mass. The irradiation luminosity required to account for the observed day-side temperature of the companion star is consistent with the spin-down luminosity of a millisecond radio pulsar. The flux decrease and spectral evolution of the quiescent optical emission observed comparing our data with previous observations, collected over 5 years, cannot be well explained with the contribution of an irradiated companion star and an accretion disc alone. The progressive flux decrease as the system gets bluer could be due to a continuum component evolving towards a lower, bluer spectrum. While most of the continuum component is likely due to the disc, we do not expect it to become bluer in quiescence. Hence we hypothesize that an additional component, such as synchrotron emission from a jet was contributing significantly in the earlier data obtained during quiescence and then progressively fading or moving its break frequency toward longer wavelengths.Comment: 7 pages, 8 figures, accepted for publication in Section 7. Stellar structure and evolution of Astronomy and Astrophysic

Modification of carbon by diazonium Salts: control using a radical scavenger

International audienc

Modification of carbon by diazonium salts: control using a radical scavenger

Grafting of organic structures using the diazonium chemistry is a recognized method for obtaining functionalized surfaces.1 Various conducting materials as metals and carbon can be modified in aprotic or aqueous media, and provide covalently tethered layers. The efficiency of this grafting process rests upon the high reactivity of the aryl radicals produced at the electrode-solution interface. This reactivity leads to the generation of polyaryl layers via the radicalar attack of already grafted aryl species on the surface. As a consequence, the method routinely provides disordered organic films having a thickness varying from one to fifty nanometers. The lack of control, in terms of thickness and organization, represents the major drawback of this elegant and versatile technique. A simple strategy to avoid the formation of polyaryl layer during the functionalization of carbon surface by diazonium reduction is presented.2 The approach proposes to directly act on the polymerization mechanism by the use of a radical scavenger (DPPH = 2,2-diphenyl-1-picrylhydrazyl). The kinetic gap between the surface coupling and the multilayer formation is exploited to prevent the growth of the layer without interfering with the grafting

Modification de surfaces par réduction de sels de diazoniums : contrôle du greffage via la chimie radicalaire

Bien qu’étant de plus en plus utilisée depuis dix ans, la modification de surface par réduction de sels de diazonium reste mal maîtrisée en raison du faible nombre d’études fondamentales menées et des difficultés de caractérisation physico-chimique. En effet la haute réactivité des radicaux formés lors de la réduction des cations diazonium a pour effet de systématiquement conduire à la formation d’un film organique désorganisé et d’épaisseur aléatoire. Ce manque de contrôle représente un inconvénient majeur pour la réalisation de couches à fonctionnalité avancée. Actuellement, la limitation de croissances des couches organiques est réalisée par utilisation de précurseurs à fort encombrement stérique1 ou par la génération électrochimique des précurseurs diazotés à l’interface électrode/solution2. Dans les deux cas, la synthèse des précurseurs est limitante et ne permet pas d’étendre la technique à de nombreux autres sels de diazoniums. Nous présentons  ici une nouvelle stratégie visant à introduire un radical libre, la 2,2-diphényl-1-picrylhydrazyl (DPPH) lors de l’étape de greffage dans le but de stopper sélectivement la croissance de couche sans affecter le greffage

Grafting via diazonium chemistry: controlling the multilayer formation by using radical scavengers

International audienc

Electrografting via Diazonium Chemistry: From Multilayer to Monolayer Using Radical Scavenger

A simple strategy to avoid the formation of polyaryl layer during the functionalization of carbon surface by diazonium electroreduction is presented. The approach proposes to directly act on the polymerization mechanism by the use of a radical scavenger. The kinetic gap between the surface coupling and the multilayer formation is exploited to prevent the growth of the layer without interfering with the grafting. The well-known 4-nitrobenzenediazonium electrografting was used to demonstrate the possibility of reaching a monolayer surface coverage with an excess of DPPH (2,2-diphenyl-1-picrylhydrazyl). Experimental conditions were varied to validate the efficiency of the grafting limitation and the radical capture was confirmed by isolation of the aryl radical/DPPH coupling product