Relationship between flash points of some binary base oils and their constituent oils

Miscellaneous binary blends containing solvent neutral-150 (SN-150), solvent neutral-500 (SN-500), Bright Stock-150 (BS-150), polyalphaolephin-6 (PAO-6), PAO-100, a processed low sulfur waxy material, and polyisobutene-600 (PIB-600) were prepared and their corresponding flash point (FP) were measured. By using the measured FP data, the plots of FP vs. weight percentage of minor component were drawn and the equations due to each plot were derived. Except PIB-600 containing mixtures, linear relation between FP of blends and weight percentage of constituents has been observed. Also the obtained data indicate that except PIB-600 containing blends the FP of such mixtures can be calculated from the summation of "FP × weight ratio" of each component. In the case of PIB-600 containing blends, nonlinear and decreasing, nonlinear and increasing were observed as well as constant trends of FP vs. weight percentage of minor component. The observations have been interpreted based on the composition, molecular weight, and interactions of the constituents of the base oils. KEY WORDS: Flash point, Binary lubricants, Tribotests, Mineral oils, Synthetic oils, Semisynthetic oils Bull. Chem. Soc. Ethiop. 2015, 29(2), 229-237DOI: http://dx.doi.org/10.4314/bcse.v29i2.

Direct acetylation of sunflower oil in the presence of boron trioxide catalyst and the adduct usage as the base stock and lubricant additive

Lubrication properties of sunflower oil have been modified by epoxidation in the first step and acetylation of the obtained epoxide in the second step. Epoxidation has been followed in dichloromethane solution in the presence of hydrogen peroxide and acetic acid as oxidizing agent and sulfuric acid as catalyst. The reaction has been monitored and optimized by measurement of iodine value, epoxy content, and recording the FTIR spectrum at different experimental conditions. Acetylation has been performed by enduring the optimized conditions of epoxidation reaction, in the presence of boron trioxide as catalyst and at elevated temperature. The recent reaction has been monitored and optimized by measurement of hydroxyl value, epoxy content, and recording the FTIR spectrum at different experimental conditions. The final product of both,epoxidation and acetylation reactions has been confirmed by FTIR and NMR data. Relative to sunflower oil, pour point and oxidation stability of the modified oil has considerably been improved. The modified oil has successfully been employed in the formulation of industrial gear oil. The investigation on the possibility of the additive application of the modified oil, as well as its miscibility with additives was considered

Uncovering the stellar structure of the dusty star-forming galaxy GN20 at z=4.055 with MIRI/JWST

Luminous infrared galaxies at high redshifts ($z$>4) include extreme starbursts that build their stellar mass over short periods of time (>100 Myr). These galaxies are considered to be the progenitors of massive quiescent galaxies at intermediate redshifts ($z\sim$2) but their stellar structure and buildup is unknown. Here, we present the first spatially resolved near-infrared imaging of GN20, one of the most luminous dusty star-forming galaxies known to date, observed at an epoch when the Universe was only 1.5 Gyr old. The 5.6$\mu$m image taken with the JWST Mid-Infrared Instrument (MIRI/JWST) shows that GN20 is a very luminous galaxy (M$_\mathrm{1.1\mu m,AB}$=$-$25.01), with a stellar structure composed of a conspicuous central source and an extended envelope. The central source is an unresolved nucleus that carries 9% of the total flux. The nucleus is co-aligned with the peak of the cold dust emission, and offset by 3.9 kpc from the ultraviolet stellar emission. The diffuse stellar envelope is similar in size to the clumpy CO molecular gas distribution. The centroid of the stellar envelope is offset by 1 kpc from the unresolved nucleus, suggesting GN20 is involved in an interaction or merger event supported by its location as the brightest galaxy in a proto-cluster. The stellar size of GN20 is larger by a factor of about 3-5 than known spheroids, disks, and irregulars at $z\sim$4, while its size and low S\'ersic index are similar to those measured in dusty, infrared luminous galaxies at $z\sim$2 of the same mass. GN20 has all the ingredients necessary for evolving into a massive spheroidal quiescent galaxy at intermediate $z$: it is a large, luminous galaxy at $z$=4.05 involved in a short and massive starburst centred in the stellar nucleus and extended over the entire galaxy, out to radii of 4 kpc, and likely induced by the interaction or merger with a member of the proto-cluster.Comment: 7 pages, 4 figure

Strong (Hb + [OIII]) and Ha emitters at redshift z ~ 7-8 unveiled with JWST/NIRCam and MIRI imaging in the Hubble eXtreme Deep Field (XDF)

The JWST is revolutionizing the study of high-redshift galaxies by providing for the first time a high-sensitivity view of the early Universe at infrared wavelengths, both with its Near Infrared Camera (NIRCam) and Mid Infrared Instrument (MIRI). In this paper, we make use of medium and broad-band NIRCam imaging, as well as ultra-deep MIRI 5.6 microns imaging, in the Hubble eXtreme Deep Field (XDF) to identify prominent line emitters at z ~ 7-8. Out of a total of 58 galaxies at z ~ 7-8, we find 18 robust candidates (~31%) for prominent (Hb + [OIII]) emitters, based on their enhanced fluxes in the F430M and F444W filters, with rest-frame EW(Hb + [OIII]) ~ 87 - 2100 A. Among these emitters, 16 lie on the MIRI coverage area and 12 show a clear flux excess at 5.6 microns, indicating the simultaneous presence of a prominent Ha emission line with rest-frame EW(Ha) ~ 200 - 3000 A. This is the first time that Ha emission can be detected in individual galaxies at z>7. The Ha line, when present, allows us to separate the contributions of the Hb and [OIII] emission lines to the (Hb + [OIII]) complex and derive Ha-based star formation rates (SFRs). We find that in some cases [OIII]/Hb > 1, suggesting low metallicities, but a few have [OIII]/Hb < 1, so the NIRCam flux excess is mainly driven by Hb. The vast majority of prominent line emitters are very young starbursts or galaxies on their way to/from the starburst cloud. They make for a cosmic SFR density log10(SFRD_Ha / Msun yr^-1 Mpc^-3) ~ 2.35, which is about a third of the total value at z ~ 7-8. Therefore, the strong Ha emitters likely had an important role in reionization.Comment: 15 pages, 9 figures. Submitted to Ap

JWST detection of heavy neutron capture elements in a compact object merger

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs), sources of high-frequency gravitational waves and likely production sites for heavy element nucleosynthesis via rapid neutron capture (the r-process). These heavy elements include some of great geophysical, biological and cultural importance, such as thorium, iodine and gold. Here we present observations of the exceptionally bright gamma-ray burst GRB 230307A. We show that GRB 230307A belongs to the class of long-duration gamma-ray bursts associated with compact object mergers, and contains a kilonova similar to AT2017gfo, associated with the gravitational-wave merger GW170817. We obtained James Webb Space Telescope mid-infrared (mid-IR) imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns which we interpret as tellurium (atomic mass A=130), and a very red source, emitting most of its light in the mid-IR due to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy element nucleosynthesis across the Universe.Comment: Submitted. Comments welcome! Nature (2023

Heavy element production in a compact object merger observed by JWST

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs) 1, sources of high-frequency gravitational waves (GWs) 2 and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process) 3. Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers 4–6 and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs. 7–12). We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns, which we interpret as tellurium (atomic mass A = 130) and a very red source, emitting most of its light in the mid-infrared owing to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe